I and another friend had problems with paying for TELCEL at Oxxo. One payment was not credited to my fone, I suspect it went elsewhere. I did not watch closely as the number was entered, got a receipt etc. My friend updated 2 fones, was not credited.
Went to another Oxxo. I watched the terminal as the number was entered. Had to tell the girl a couple of times the entry of my number was not complete. Finalyl she did the right thing.
Starting to suspect Oxxo software for a Telcel payment has a flaw that can be exploited. Pay attention.