Charged $50 for International Call I Never Made

Posting this after lurking to see if others have had the same issue. The other posts I've seen on this include details about international wifi calling or data passes. In this case I'm in the U.S. being charged for calls to the UK and I can say with certainty I never made an international call of any kind. I don't know anyone overseas and I'm positive no one called me. In fact, it's all in black and white in my account's call log - nothing there.

T-Mobile says they have "confirmed that the call and charge are valid" but can't tell me how or where I can see that information. The first two reps said there's nothing they could do for me. The third rep I got ahold of was wonderful and refunded the $50 but told me it's a one time thing and not to expect a refund if this happens again. I thanked him but the whole thing was totally ridiculous and if it does happen again I'll just cancel my service. I'm getting my next bill soon so we'll see.

Has anyone else had blatantly fabricated charges like this? No wifi calling, no data passes. Just a straight up billing error they refused to acknowledge?