Getting phone related service supplier to work fast isn't easy no matter who you are with. I don't think it helps that few have control over the whole system so are dependent on other companies to check their bit some of the time.
If it is any consolation I presently have no home broadband (nor phone) since BT failed to send their bill (4 times now) blamed me for not receiving it and paying it, and without warning cut me off. (For over a week now.)
Problem also is that it could be a number of things, some of which are yours (PC/router/modem) some the line provider, and some the Internet provider. I note you have tried a new "orange box" but generally, if you have spare equipment you could try a different PC, different router, different modem, etc. and see if the problem goes away. You could try plugging it al into a different phone socket. Are you using the main one ? Try taking off other phones in case something connected is causing a problem.
Aside from that I guess you can only sit tight and hope they solve it more quickly than the time they gave you (which hopefully is a worst case scenario - maybe).