I bought a Samsung Galaxy S4 for my Mom for $50. It came with 2 batteries and seems to be in great working order other than the fact that it won't charge. It looks like either there is a bunch of lint or something in the USB connector port or it's just completely shot. One or the other. Looks pretty shot to me. I've attached a pic. My questions to you guys are: 1 - What part do I need to fix it? 2 - Phone is locked to AT&T, but can she use it on Straight Talk's AT&T plan? This will be her first smart phone and first real try at using the internet and I want to help her out. Any help would be appreciated. Thanks in advance.