TiVo Roamio and Premiere with Charter cable, tuning adapter

A couple of years ago, we tried to switch to Charter cable in our area from WOW because Charter had better internet speeds and some incredible pricing deals. It was a mess. They made 4 visits and countless phone calls and never could get the tuning adapters (they tried multiple TAs and CableCards over the course of several days) to work properly. They even talked to TiVo on the phone and couldn't get it working. If the TA was plugging in and on, we got some channels but not others. If we unplugged it, a different set of channels were viewable but not most of the ones before. We ended up going back to WOW as they don't use SDV and everything with the TiVo works fine.

I was wondering if anyone here could give me a 'no fail' guide on how to get a provider (especially Charter) with the tuning adapter and switched digital video to work right with the TiVo so all channels work and are viewable that comes with the package. How did you overcome this? Exactly what needs to be told to the technician and people on the phone? What is the common snag that happens with these?

I'd really like to jump on their latest offer. It would save me hundreds over the 3-year price lock-in, plus WOW has been unable to solve a problem where our internet drops out for a few minutes multiple times a day.

Thanks in advance!