Caller hears loud buzzing when I answer phone

[ladysaotome]

I have a G925A AT&T version - unlocked. I've been using it on Straight Talk for the past year with no problems. Switched to T-Mobile last week and everything seems to have been going fine. However my husband has had issues where nearly every time he calls me, he hears a very loud buzzing-static when I answer the phone and I just hear silence on my end. But the call always goes through when he tries a second time. We thought it was his cell phone (Huawei Honor 8) having problems but today he called me from his landline at work and he heard the exact same loud buzzing-static noise while I got silence. So it has to be something with my S6 Edge. I've searched online and am coming up empty and I can't even figure out if it must be a setting I need to change for T-Mobile or maybe my phone is going bad?