International roaming / India - has issues

I have been trying to use my T-mobile service on several of my trips to India over the past 10 years- Come back from each trip frustrated whenever I tries to use. In large cities it works good percentage of times, but once in the country side, and that includes National Highways, it rarely works. Initially, I spent lot of time talking to the customer service of T-mobile and also local partners. Yes, I am talking about the areas where T-mo maps show it's in the covered areas. Now I just turn it on only when I have wifi access. I understand the frequency bands used for the handsets sold in USA may be sometimes different from the ones Indian cell sites use (there are always at least some common bands where the handset should lock on), but I even tried using T-mobile sim on  Indian handsets, but still they don't work. It's same whether you buy a roaming package or use free slow speed data you get with the magenta plans - I tried both. This probably is the problem with the setup with the Indian carriers, but it's for T-mobile to coordinate with them and get it fixed. We cannot take it up with them individually where we are not even their paying customers. I don't think T-mobile cares.