I suggest you file a warranty claim to try to resolve the issue. I am using the same device and never experienced the same issue that you are having.
Desperate for a solution so here's my issue. Brand new S7 edge on Virgin Mobile Canada. Phone works flawlessly except when I place a call to a landline that busy. When I call a landline with no call waiting and someone is on the phone I should get a busy signal but do not. I get one tone of the busy signal then dead air for 35 seconds at which time it returns to normal. The odd part is that certain numbers this happens with 100 percent of the time while with other numbers its intermittent and still others it never happens to. Virgin had done extensive testing and troubleshooting and claim they're are no network issues. If I put my sim in other phones there are no issues and the problem disappears. Has anyone else experienced this or can anyone offer some suggestions as to why this may be happening. I really can't see it being a hardware issue given the symptoms but it sends to be pointing to it. Samsung has no record of this issue. Any and all suggestions will be appreciated.