Marvin, I think I owe you an apology. I was the one that suggested that you post to the open forum.
If you like to watch TV then you need to keep Dish but it should be installed at your home and you use the same receiver(s) in your RV when you travel. This costs you nothing additional. If you don't need Dish for TV then we have a different scenario. If you are paying for home phone service plus cellular phone service then you need to drop the home phone in favor of cellular only as that will work at home and when you are on the road.
Voice and messaging is generally included in all plans at no charge so whether you use it or not is not important. The plans are put together based upon data and trying to replace your Dish (any kind of TV service) with a service that requires internet is going to be much more costly than anything you are paying for now.
T-Mobile does have a very nice 55+ plan where you get 2 phones for $60/month with unlimited internet but that does not include tethering. I have heard that you can add tethering for another $20/month but there are still going to be many areas where limited or no service is available rendering ALL TV watching useless. I believe you have Dish at home and you plan to use it on the road. This is a GOOD plan. Separately, you need to consider your best options for phone and internet.