Your reply is intelligent, so I'll respond.
I've been with tmobile for 10 years or so. Not as long as you. I've always had an unlimited plan, or at least a plan so high that I never went over. A few years ago (3 or 4???) they called me out of the blue to tell me I was eligible for a lower rate. I peppered them with questions to figure out what the catch was. There was no catch. It was the same features I already had, for less money, and it was a permanent rate. Then, a year or two ago I dropped my rate again when I went to their new uncontract gimmick where you save $20/mo by not prepaying for a new phone that you might never upgrade to. Not to mention that the $20/mo fee is more than the cost of buying the phone contract-free. The way they marketed it was a complete gimmick. But for almost everybody you'll save money by dropping the $20/mo fee and buying your own phone. So yes, my rates were lowered multiple times while my service stayed the same.
In my case my service actually went up after dropping the rates down because now I have completely unlimited text on both lines, where before I had text blocked on my cell phone and only enabled on my wife's. I don't understand your comments about the 500 texts per month fee. Mine are unlimited. It's clearly unlimited in the US per the contract. Just like I can't expect to call Russia from my cell phone and not incur any extra charges (unless it is specifically listed in my contract). In foreign countries, you have to read the fine print to determine if they are free in that country or not. I believe this is a new feature that just started last summer, but maybe that's just when I found out about it. I was fortunate enough to travel to central Europe, and I can tell you that my texts were free, and so was my data service. I don't think I made any phone calls while I was over there, so I'm not sure if those would have been free.
I also don't understand your comments about overage fees and the unlimited data plans. T-Mobile's standard plan has unlimited data, plain and simple. They make it very clear that you only get a certain amount at LTE speed, and then any additional data is delivered at 3G. They actually make that part very clear so no-one can claim they were tricked. I pay a little extra so I can get enough LTE speed data that I never run out. But even if I didn't pay for the extra LTE, I would still have unlimited data (just at a slower speed). There are no overage charges for data, period. Data is unlimited. Speed is not. I greatly prefer to have it setup this way as I never have to worry about my bill. I'm not paying to get more data - that's a misnomer. I'm merely paying to get more data delivered at a higher speed. I'm not sure what you meant by it not applying to everyone. Maybe there's some old plans out there that cut you off at a certain amount? I have no idea.
Just to re-iterate, I have completely unlimited phone, data, and text on two lines for $80/month. I pay to get a bit more data delivered at higher speed for an extra $20/month. And, because T-Mobile is a worldwide company and not just US based, they allow us to use their services in specified foreign countries for free as long as we have the right type of phone (for the right frequencies in those countries). Not all countries are included, but where I went in Europe was.
If you're annoyed at overage fees, then get off the old grandfathered plans and get the new plan where everything is included. I thought for sure there was a downside to the new plans both times I switched, but there isn't. I buy my phones at retail prices, and I break even after less than two years (vs $20/mo). So even if I upgraded every two years I would still be saving money on these lower plans. And if I keep the phone for three years, then I'm just banking those savings to have more to put down on the next phone.
If you live and mostly stay in a major city with LTE coverage, there really isn't a downside. I've been to San Francisco, Vegas, and far outside Boston recently with no loss of coverage. It's a good deal.