Just relaying my recent experience in calling BT to report a problem. In each case, I texted the problem (slow or zero upload - see separate thread on the issue) per BT's recommendation. My experience was:
Monday to Friday: A bot replies, asking for permission to run tests on the line. Once granted, the this takes about 10 minutes and the bot informs you everything is perfect with the option to reply asking for an agent. If you take that option, someone from a call centre gives you a call. My experience on the last point has zero positivity.
Sunday: No bot as such. Just a reply that someone would call back soon. Had dealings with two lovely people from technical support - I'm guessing line 2 (one in Cardiff, the second in Ireland) who actually listened and tried to diagnose the problem, culminating in the second arranging a visit from Open Reach (and, fingers crossed, the result seems to be the problem is sufficiently resolved).
Now, I guess the Sunday experience may well have been to other systems being down, so caveat YMMV, but perhaps worth trying if you're banging your head against the wall with them.