stop buffering on my phone
How are you connected to the Internet if not via WiFi? 3G? Sorry, but no go.
You need to be connected to a WiFi hotspot with decent bandwidth and connectivity.
Edit: So MetroPCS supports 4G LTE. Does your phone support 4G? In that case, that should have worked... except that MetroPCS's wireless network may or may not have a good connectivity with YouTube or wherever are you watching videos.
Also, if you're watching YouTube videos... sometimes you may find poor transfer rates, mainly because of bandwidth congestion on YouTube's end. I blame the advertisers.