MAJOR Phone issues

I moved my phone system over to zoom last year and have not had any issues for the most part until here recently. I literally cannot function my business with how God awful terrible the phone reception is.  I have two different Internet providers just for this purpose and I am encountering the same terrible phone issues with both Internet providers as the phone constantly cuts out. I thought at first it was my wireless headphones, which were Apple pro headphones with my brand new MacBook Pro and I purchased a brand new wired headset, but I am still encountering call quality that makes me repeat myself 1000 times before the other person can understand what I'm saying.  I literally cannot function my business with your phone system, and I am beside myself upset and downright pissed off as moving phone carriers is not an easy task.  I don't know what to do I have tried everything and what's worse is I can't even call you to discuss this. I am sick and beyond belief.