Slow Home Internet

none of these solutions was very helpful, and tech support is not very helpful either. I wanted to know if I could A) use a wifi extender to improve signal and was hoping someone here who has same issues might have tried it, or 😎 can I buy/use my own router/modem that would work better?  I have no tolerance for internet that goes in and out and can't call tech support and be on the phone for hours, when they say they can "fix it" no worries, and then next day it doesn't work again!  The most confusing part is I have an "excellent" signal, but no wifi connection or slow internet speeds (like below 10 20) more often than not!  Calls either drop or they can't hear me.  On a speed test, it allows me to pick a closer tower, but it doesn't let me keep it at that or automatically go to that one all the time! Every time I have to reset the gateway, I have to add ALL my devices which are all time consuming steps (ie. my nest, security camera, smart lights, etc.) and I just don't have the time or patience for that!

If it's not going to work in my area yet, then they need to admit that and I can go back to my previous service, though that was more expensive and not 100% either, but at least more consistent and didn't require me to physically do all the work!  They said they still don't have a tech that could come to the house because of covid, even though I live in Florida and everyone is "open" here, some take precautions like wearing masks when they come, but not that there is "no one available" to help me! I'm willing to pay someone, but don't even know who to ask for? This is just unacceptable!