Hi, A bought a used Samsung Galaxy S5 (Verizon) from a friend of mine to upgrade my older S4. His 2 year contract was up and he upgraded to the Galaxy S7 Edge. I did some research and I thought I could stick my AT&T sim card in the S5 and go about my business. I changed my network mode to GLOBAL and turned on my Global Data Roaming Access. I thought everything was working great, but when I traveled to Galveston beach I realized I could only call and text people. Texting only worked about 50% of the time. No applications were working for example google maps, spotify, groupme etc. Everything worked when I was home because of the wifi connection. So my question to the forum is can I use the Verizon S5 with my AT&T sim card?