I have unlimited data/calling/text and 5GB of tethering per month for $50/mo with T-Mobile, but it's a grandfathered in plan that they put me on when they stopp

I have unlimited data/calling/text and 5GB of tethering per month for $50/mo with T-Mobile, but it's a grandfathered in plan that they put me on when they stopped offering plans with limited voice minutes (I had the lowest allowance possible) about two years ago.