Can I use a T-Mobile sim on a Verizon(G900V) phone?

[Bukkakemon]

Is it possible? I hear verizon runs on CDMA while Tmo is GSM. Or does a custom rom help?

 

[hallux]

The G900V only supports bands 4 and 13 for 4G data, you'd have to find out what bands T-Mobile uses in your area.

No, a custom ROM will not help as you need the hardware to support the radios T-Mobile uses. Also - it may not support the technology needed for voice calls.

See here for all the radio specs - Samsung Galaxy S5 (USA) - Full phone specifications