Within the past month I picked up an HTC One M8 on sprint, huge mistake. Sprint service never comes through the tri-band antenna in this phone. No calls In or out and ZERO data; and I know it is not the phone because this is my second one! I normally have to use my friends AT&T hot spot in order to do anything. So, out of curiosity would it be possible to use the Sprint M8 on an AT&T go phone plan? Any information would be very much appreciated!
Unfortunately, no, the technologies utilized by the Sprint version of the One M8 are not the same as the AT&T variant. AT&T (and T-Mobile) uses GSM technology, while Sprint (and Verizon) uses CDMA. Therefore, because of these differences in network technologies, your phone would be incompatible for use on AT&T's network - prepaid or postpaid.
For some reason, Verizon-locked iPhones have the ability to work on AT&T's network, but not the other way around. I'm not sure if this applies to select Android devices.
The Sprint M8 does have a GSM radio inside it. However Sprint programs its devices at the hardware level to block GSM networks in the United States (Such as AT&T and T-Mobile). Additionally the LTE Bands are not LTE so even if everything was able to work you would be getting only 2G speeds.
All Verizon iPhone 5, 5C and 5S phones are SIM unlocked for unrestricted International and Domestic use. Only the CDMA radio is locked down to not work on any other CDMA network (such as Sprint). I have saw that Verizon also does the same thing Sprint does with their Android phones, but mostly in the "Droid" lineup.
I would suggest selling your M8 and buying a new GSM one. With how new it is you should be able to get a pretty good amount for it.
Hope this helps!
*I am an AT&T employee and the postings on this site are my own and don't necessarily represent AT&T's position, strategies or opinions.