Poor Signal Annoying

I have been using Rain for 18 months and at first it was great until last month when I started enquiring about their 5G router and after that enquiry my current 4G signal is wack. I don't know if this is some way to force me to upgrade or not but I am so sick and tired of the poor signal and nobody is able to reach out and assist you, it is a nightmare getting through to the call centre.