Cell-Plan Pruning — Phone Bill Audit & Carrier-Switch Math

Overview

Phone bills inflate silently: a family plan sized for a teenage-streaming era, $15–$25/line "device protection" on phones worth $150, per-line insurance bought at flagship launch and never revisited, upgrade fees, and the assumption that switching is a hassle that keeps people paying $40–$60/line for usage an MVNO would carry at $15–$25.

This skill audits a bill (paste the line items) against actual usage reality (per-line data consumption, phone ages/values), classifies every recurring charge KEEP / DOWNGRADE / DROP / SWITCH, and computes the honest annual savings of each action — including the switching costs (taxes/fees differences, eSIM activation, phone-lock status, trade-in treadmill exit).

When to Use

• "My phone bill is $220/month for 4 lines — is that bad?" (it is)
• Considering MVNO switch (Mint/US Mobile/Tello/Visible/Boost...) vs premium carrier
• Reviewing whether device-protection/insurance lines are worth it on current phone values
• Kids/parents joining or leaving a family plan; a line nobody uses anymore
• Comparing prepaid vs postpaid for the same usage
• Don't use for: phone purchase decisions per se (that's phone-shopping), international roaming trips (travel eSIM skill territory), or enterprise/business fleet plans

Core Knowledge

1. The bill anatomy and where the fat is

bill = base plan (bucket) + per-line access fees + device protection × N
     + add-ons (cloud, AppleCare-ish, premium visual voicemail) + taxes/fees (~15-25%)

Typical fat, in order of size:

1. Oversized data bucket — median household usage is well under what people pay for; "unlimited" is a comfort purchase for most light users
2. Insurance on old phones — $15/mo × 24 mo = $360 + deductible $150–$300 on a phone worth $200. Breakeven math almost always says drop after year 2
3. Per-line access fees on postpaid — $20–$40/line that MVNOs simply don't charge
4. The upgrade treadmill — carrier "free" phones are financed into the plan; leaving means paying the balance. Exiting the treadmill is the biggest structural save

2. Per-line data reality (the audit's core input)

Pull 3–6 months of per-line usage from the carrier app. Classify each line:

• Light (<5 GB/mo): WiFi-heavy, music/podcast user → MVNO pooled or capped plan
• Medium (5–15 GB): occasional video, maps → mid-tier MVNO
• Heavy (>15 GB consistently): commuter streaming, tethering → unlimited tier justified — or premium-deprioritized unlimited (fine for most)

Then compare bucket size vs sum of actuals + 20% headroom. Most families find they pay for 2–3× their usage.

3. MVNO truth table (US market, typical)

MVNOs ride the same towers (coverage = host network), with trade-offs:

• Deprioritization under congestion (rarely noticeable outside stadiums/airports)
• Hotspot caps (often 5–10 GB even on "unlimited")
• No roaming fanciness, weaker international rates (usually)
• Fewer perks (no "free" streaming bundles)
• Phone must be carrier-unlocked & paid off; eSIM makes switching same-day

4. Device protection decision rule

keep if: monthly×18 + deductible < 40% of current replacement value
drop if: phone age > 24 mo or replacement value < $400
alternative: self-insure (put the premium in a jar) after year 2

The script computes this per line from phone age + model value.

5. Switching friction checklist

• Phones unlocked + installment balances paid (or accept payoff)
• Number porting: do NOT cancel first — port-out cancels the line automatically; get the account number + PIN/transfer PIN (postpaid likes to hide these)
• eSIM: activation minutes, not days; physical SIM fallback
• Taxes/fees differ by plan type — compare all-in prices (script takes tax % for both)
• Watch promo credits: "30 bill credits" — leaving early claws them back

Workflow

1. Collect the bill: every recurring line + amounts, number of lines, per-line usage (3–6 mo average), phone ages + rough resale values, current insurance cost/line.
2. Audit:

   python3 scripts/plan_pruner.py --demo
   python3 scripts/plan_pruner.py --bill bill.json      # your data, see bill.example.json
   

3. Read verdicts per line-item and per phone-line: KEEP/DOWNGRADE/DROP/SWITCH with $/yr each.
4. Sanity-gate before switching: coverage on the target MVNO's host network where you live (coverage map + a friend's phone test), hotspot caps OK for your use, phone unlocked.
5. Execute pruning in order (no-switch steps first): drop insurance on old phones, remove add-ons, downgrade bucket, then the MVNO decision as the last move.
6. Port correctly: new carrier initiates the port with account # + transfer PIN; lines port one at a time if family members want to stagger.

Common Pitfalls

1. Comparing sticker prices, not all-in. Postpaid "unlimited $65" is $78+ after taxes/fees; some prepaid prices are tax-inclusive. Always compare final monthly totals.
2. Keeping insurance by inertia. The premium+deductible on a 2.5-year-old phone exceeds its replacement value within 18 months. The script flags this per line.
3. Ignoring installment-lock reality. "0% financing" with 20 remaining months = you owe it at port-out. Promo credits cancel too. Compute the exit cost before declaring savings.
4. Dropping the whole family to a 2 GB shared plan because averages looked small — one heavy line ruins it. Prune per-line, not per-family.
5. Porting wrong: canceling the old line first kills the number. The NEW carrier's port process does the canceling.
6. Chasing a promo price with a 3-month teaser that reverts. MVNO pricing is often flat; premium-carrier promos are often time-boxed credits. Model the steady state.

Verification Checklist

• Every recurring bill line classified KEEP / DOWNGRADE / DROP / SWITCH with $/yr
• Per-line data usage tabulated (3–6 month average, not one month)
• Bucket vs actual usage gap computed (×2/×3 oversize flag)
• Insurance breakeven computed per phone (age + value vs premium + deductible)
• Exit costs included in the switch math (installment balances, lost promo credits)
• Target network coverage verified where the user lives/works
• Annual savings total stated as the sum of independently-executable actions

One-Shot Recipe: 4-line family at $327/mo all-in

Lines: 2 adults (8–12 GB), 1 teen (26 GB), 1 grandparent (1.5 GB). Bill: unlimited premium ×4, insurance on 2 phones ($17/ea), $10 cloud + $5 voicemail add-ons. Audit: grandparent → LIGHT capped MVNO line (~$25 all-in, −$355/yr), adults → MEDIUM mid-tier (−$494/ea), teen → HEAVY unlimited is justified but an MVNO unlimited tier carries it (−$302); insurance: both phones fail the 40%-of-value breakeven (18-mo premium+deductible $506 vs values $320/$900) → DROP (−$481); add-ons → free-tier equivalents (−$212). Result: $327 → ~$132/mo ≈ $2,338/yr saved with zero behavior change and the same towers.