It seems Google has decided to reward T-Mobile customers that signed up for Google One, because customers are beginning to receive emails offering $10 Google Play credits.
The offer is part of the “Google One Benefits” program that offers occasional perks to Google One subscribers. The $10 Play Store credit, offered via an email like the one below, appears to specifically be for customers that signed up via T-Mobile.
T-Mobile and Google announced a tighter partnership back in March. Then, in October, T-Mobile announced a unique Google One plan available only to T-Mobile postpaid customers. The carrier-specific plan offers 500 GB of Google One cloud storage for $5 per month. Customers also have the option of signing up for the 2 TB plan for $10 per month via the carrier, however that plan is not unique to T-Mobile customers.
If you have a Google One subscription, be sure to check your email for the offer. You can also try opening the Google One benefits page directly and redeem it there.
The promotional offer is valid until April 1st, 2022, and the promotional value must be used by July 1st.