"It's not my isp because neighbors have no issue "
This statement is very wrong. The fact that your neighbours (even if they have the same ISP), dont have issues doesn't mean it can't be the ISP.
The ISP is responsable for everything from your home socket, to the neighbourhood switching boards and onwards.
with the servicelight flashing red, I assume you mean the light on your router. That means that it likely is something in the neighbourhood switchboard.
Wether or not the costs for that are for your ISP or for you depend a lot on national laws an customs.. I do think this is not the right place to get help. Just saying that I had a simular issue (with a different ISP in a different country) and it was fixed by the ISP and it was a bad connection in the neighbourhood switchboard.
Through me you pass into the city of woe:
Through me you pass into eternal pain:
Through me among the people lost for aye.
With at&t anything from the outside terminal in is customer owned . Just like with a power line . Meter to house is customer owned , the water meter to house and sewer from curb to home. If they do anything past these points they bill you even if they setup anything past these points . Calling them is the biggest pain and I sub for their company lol