WiFi been dropping several times a day

What can I do with this? 

Constantly dropping out of service at various points of the day. Not hitting anywhere near the speeds thats meant to be getting either when it is up?

Never had problems in several years but the past 2 months this has been a massive problem.

Any advice moving forwards. The website constantly says check back in 24 hours and we will arrange an engineer.  Same message every day.