iPhone 7 unlocked A1660

I bought an unlocked iPhone 7 model number A1660 from the US. I’m in my hometown Yemen and trying to use it with CDMA carrier which is YemenMobile but I couldn’t. When I put a GSM SIM it works right away. But when I put my YemenMobile SIM which is CDMA its showing the name of the company when I go to About>Network but there is no signal it keeps saying No service. I tried to Reset the Phone and restore using iTunes but still the same problem. FYI, my brother bought the same phone same model number and it was locked for verizon that was a year ago and its working just fine. I conacted Apple and they confirmed that the phone is compatible with both GSM and CDMA. I also contacted the carrier and they provided the latest network settings but still not working. What really makes me frustrated that my brother’s phone is the same model as mine. Anyone can help me please!