Can I use any tmobile iphone6s on metro, seeing as they are connected? Im looking to get a 6s used off of swappa.com, and I can save a few by getting a tmobile iphone 6s rather than an unlocked variant. And if it comes locked, is there anyway I can unlock it?

So it started about a month ago, i think when my father bought me a bad charger and everything started getting messy. I have around 20,000 pictures,my phone basically deletes them then restores them and sometimes it shows the pictures as grey boxes too,also my touch is messed up it clicks on...