Loss of signal

[Sissichic]

I just started my services back in March at my new home I juat bought. The tech came and installed my internet and everything was working fine. Then since 5/27 I have been having connection issues like crazy. My modem will stay connected for 30mins the lose signal.  I call, text and every rep tells me they will resend a signal and this should work. I have replaced my modem three times already in the past week. Still continues with the same issue. I have had a tech come out and change a wire that was in my home still the same issue. It has gotten so bad I had to get services with ATT just to be able to work from home. I am not sure what else we can do. I do not believe it is not the modem I think it has something to do with lines outside or maybe it is the modem. I would like to know how to fix this or what should i be looking for to let the tech know. Please help, 

[EG]

Start here;

https://forums.xfinity.com/t5/Your-Home-Network/Internet-Troubleshooting-Tips/m-p/3310447#M316652