Need some advice for ending my contract, & what next? ...

Sprint will require you to port your mobile # out to another carrier.

ETF=early termination fees. The carrier will penalize you for ending your conctract early, and the price can vary a little. Call Sprint to find out exactly how much this will cost. It sort of bites you in the bottom if you prorate that cost vs. the arguably more modest increases in fees over a fixed period, assuming you are well into a two year contract.

If you do determine it's cheaper for you to pay the ETF, don't port the new number anywhere until you are completely satisfied with the new carrier/service. Take a few weeks to evaluate both service and new handset/features offered by the new carrier, especially considering it will likely be a contract arrangement again. Consider the number they assign you as a temporary one. Once you are happy, *then* port over your old Sprint number. This way you won't make the mistake of immediately porting to something you do not like and losing your old valuable contact number forever.

Moving to a prepaid phone still won't get you out of paying an ETF, FWIW.