A:Answer Hi fellow costumer,
I understand your frustration with being unable to purchase a T-Mobile iPhone 15 through Best Buy. I'm not sure what the issues are between the two companies, but it is unfortunate for customers.
To answer your question, yes, Best Buy will provide AppleCare with TotalTech membership for an iPhone purchased from Apple. TotalTech covers all Apple devices, regardless of where they were purchased, if the purchase was made while you have an active membership.
I hope this information is helpful. Please let me know if you have any other questions.
I hope you're able to get your new iPhone soon, and that you enjoy the peace of mind that comes with having AppleCare protection!