020 3781 1528 Negative Who called me from this phone number?

Indian woman claiming to be from testosterone mobile saying my sim was being disconnected. Obviously a scam

Said they are from o2 and that my sim isn't compatible with 5g and that I need to tell them the one time code. The first time they phoned I refused to give it stating the text message said not to share it. She went on to say I can give her the code but if anyone phones after her I shouldn't give it. I refused. The next say another call answered it hands free as I was driving said the same thing said to give them the one time code I said well I can't as I'm driving she said could I not put the call on hands free and read the text message to this I just laughed and said absolutely not as I'm driving they said it won't take long ... they then said I was going to get a call the next day. No phone calls the next day then today 7 missed calls. Glad I checked on here as I will now string them along if they call again

Has persistently called me every day over the last week. One time I answered just to be sure and the line takes a few seconds to connect to a person. This indicates it's a robot caller that only connects to a person when someone answers. The person said they are from O2 because my SIM will be getting disconnected. This is utter nonsense so I told her she's lying to me and the call didn't go much further.

An Indian lady called me claiming they were from O2, saying my SIM was being disconnected as it's not compatible with 5g, sent me a one time passcode and asked me to read it out over the phone. O2 themselves say to never share a one time passcode with anyone, not even an O2 employee.