Hi, thank you for your note! Could you expand a bit what you meant with “T mobile”?

Is this public telephone still working? All public telephones in Germany have been switched off. See also the discussion in https://community.openstreetmap.org/t/anfang-2023-werden-alle-offentlichen-telefone-der-telekom-in-de-abgeschaltet/4712.

If the hardware is still there but cannot be used anymore, it should be retagged as disused:amenity=telephone.

Or did you mean that this is not a T-mobile Wifi hotspot? In that case it should be retagged as such.