I switched to Mint Mobile, 10 days before my cycle ended. Taking my automated payment off-line as well. Thinking they'd send me a final bill. They did and I paid it online, and if any late charges were owed it should've been stated then.
Two days later they issued late charges and I received a bill for a partial month, fees, taxes, and nondescript charges.
Calling them on the phone was a waste on time, but I figured they had it coming, as I blew up several reps calling queue ratios. I couldn't recall a frick-en 6 pin number. The various reps (4 in total) kept repeating that I'd have to travel 20 minutes away to the corporate store, not a franchise store.
They can suck wind about the late and the sundry of other charges. I'm not concerned financially about any credit report. It's the point of the matter, they're outsourced and don't give a sheit about how well they provide customer service, though they'll tell you white lies the entire time on the phone.
Recommendation: Go to Mint Mobile, most areas are on a better cellular source, Verizon cell towers as primary.