T-Mobile breaking promises to seniors who were offered price-lock guarantee for life on 55+ rate plans

In 2017, we signed up for the T-Mobile One program at Costco.
I just spoke with a Costco rep, and he spent quite a lot of time looking into this. His suggestion is that I (and any of you who signed up at Costco) complete the online Feedback form on the Costco.com website home page. This is the comment I left: You are welcome to use it (or a version of it):
 

In 2017, we signed up for the T-Mobile One program at Costco, a rate plan for customers 55+ that promised the $30 per month rate would "never" go up. We switched from AT&T and moved my mother over, also. This past week T-Mobile One customers were advised that their plan was going to be increased $5 per line per month. I have spoken to T-Mobile, but there are no options for us at the same rate.

I just spoke with a Costco rep, and he spent quite a lot of time looking into this. His suggestion is that I (and anyone who signed up at Costco) complete the online Feedback form on the Costco.com website home page. This is clearly a T-Mobile issue, but having engaged in a contract with a Costco contract vendor, we expect the same adherence to contractual promises made as we do with any Costco product.

We hope you can help us and the thousands of other Costco customers who signed up for this plan at a Costco store.