Plan comparisons are honest about monthly price and quiet about everything else. Switching has a one-time cost, and if you don't know what it is you can't tell whether a cheaper plan is actually cheaper. None of these are reasons not to switch — they're reasons to know your break-even month before you start.
Forfeited device credits
This is almost always the biggest one. Postpaid promotions pay for phones as monthly bill credits spread across 24 or 36 months. Those credits are contingent on staying on a qualifying plan, so the day you port out they stop — and the remaining device balance becomes due in full.
The remaining balance on a financed phone
Separate from credits: if the handset itself is on an installment plan, leaving accelerates it. You keep the phone, but you pay the rest now rather than monthly, and it stays carrier-locked until it's settled.
Activation, SIM and upgrade fees
- Activation or upgrade fees on postpaid lines are commonly $35 per line and are rarely waived without asking.
- Physical SIM kits carry a small charge at some carriers; eSIM activation is usually free, which is one quiet argument for eSIM.
- Prepaid brands typically skip activation fees entirely — worth weighting in the comparison.
The overlap month
Postpaid billing is not prorated at every carrier. If you leave three days into a cycle you may still owe the full month, while the new carrier has already begun charging. Budget for paying two bills once, and time the switch just after a billing date closes rather than just before.
Losing bundle and multi-line pricing
Pulling one line out of a family plan can raise the per-line price for everyone left behind, and home-internet bundle discounts often depend on an active wireless line. The saving on your line can be smaller than the increase on the account you left.
Perks you were quietly using
Streaming subscriptions, cloud storage, international roaming allowances and hotspot buckets bundled into a postpaid plan have a real replacement cost. If a plan included a streaming service you'd otherwise pay for, subtract that from the saving honestly.
The costs people overestimate
Two things are usually cheaper than feared: porting a number is free, and early termination fees are largely gone from consumer wireless — what replaced them is the device-credit forfeiture above. If a carrier quotes you an ETF on a modern plan, ask them to identify it on the contract.
Working out your break-even
Add the forfeited credits, remaining device balance, activation fees and the overlap month into a single one-time figure. Divide it by your monthly saving. That's the number of months before the switch is ahead — and if it's longer than you expect to keep the plan, the cheaper plan isn't cheaper.
Taxes and fees included, so the monthly number is the real one.
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Jean Gilles has researched personal finance, consumer technology, and wireless pricing for over a decade. He founded ShopCellPlans in 2019 and writes every review on the site.
Frequently asked questions
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