Need technician visit, no wifi, no ethernet nothing.

Hi. For the past year my wifi has been dropping every 30 seconds, needing to reconnect to gain internet access again. Now, for the past few weeks the same is happening with all wired in devices too. 
Today, I was advised to disable smart switch and split the 2.4Ghz and 5Ghz networks. I disabled smart switch which has now crashed my entire network and given me an error ‘the service may be interrupted’ and left me with no internet at all (for an hour now and counting).
These have been ongoing issues for a year with 3 technician visits that temporarily fix the issue only to have it start up again a few weeks later.
I’m paying for the top package which includes up to 3 extenders and still am yet to receive them, meaning 4 rooms in my house are dark zones. I’m entitled to £100 cashback but can’t even test the rooms in app as I can’t get a stable enough connection to even scan them, it fails mid way. 
Please, book a technician visit. I’ve tried everything you’ve suggested. I was previously told I had third party extenders plugged in and a forum member refused to help because of it. The only thing I have is a tp link device to split one ethernet cable to five ports , for my consoles.