AT&T HAS BLOCKED MY BIZ PHONE LINE FROM SENDING OUR CUSTOMERS TEXT MESSAGES IF THEY ARE AN AT&T CUSTOMER

I am an AT&T customer and have been for years with multiple lines and a heavy monthly bill. I use a different online phone service for our company main phone line. We are a vacation rental company and we use texting quite a bit. Sometimes we send similar texts out when sending guests similar (yet unique) info like their property access codes. In the last week, I guess activity like this has caused AT&T to think we are spamming phone lines, but WE ARE NOT. We now are receiving messages from AT&T users, but cannot respond. They think we are just not responding and this is hurting our biz terribly!! We need immediate help PLEASE. We have registered with HIYA, but how do we get our non-spamming number off AT&T's spam number list?? PLEASE GET ME TO SOMEONE IN AT&T WHO CAN HELP!