“T‑Mobile will never change the price you pay for your T‑Mobile ONE plan.” That was the promise. The Un-contract. The whole reason millions of customers picked the magenta team over Verizon and AT&T in the first place. Now T-Mobile is retiring legacy 3G and 4G-era plans — Magenta, ONE, Simple Choice — and automatically moving customers onto “modern” 5G plans at higher monthly costs. Billing changes hit mid-July for the current wave. The company that swore it would never surprise you with a rate hike just sent the notification.
On the backup line you can subscribe to the cheapest data-only plan for like $5 a month and then just add $20 worth of pay-as-you-go credit, which never expires and will be used for calls, at 1 cent per minute.
It will save you $5 a month on the backup phone plan, making it even cheaper.