Is it possible that i may have messed up the phone?

I have had an OPO since 2014 november, and since then, i have had install many various roms. But since august and i installed official cm12.1, my phone stopped working properly. While the phone is just idle on lte, when i get a call, i see the antenna change back to 3g but i dont get the call, and couple seconds later for the caller, call goes to voicemail. Or when i try to make a call on lte, most times, it doesnt connect like it cant properly work on 3g networks. When im on 2g everything works fine. But obviously i dont wanna get stuck on 2g. Also, i have tried probably every possible related thread and method, including going stock, going cm11s ( first official stock rom), installing different recoveries (twrp 2.8.6.0, 2.8.7.0.5 materialized, philz) and the modems and basebands even with fastboot. And nothing seemed to worked for me. So i was just wondering if i did mess up my phone or my phones modem or/and antenna. And how would i know for sure? Btw i also tried different sims. No luck.

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