Missed call on mobile (UK)

Called back and told "Sorry but this mailbox is full and cannot accept messages" in an American accent. Hope I don't get charged for it.
So annoying

+2030063103
o2
Called back and told "Sorry but this mailbox is full and cannot accept messages" in an American accent. Hope I don't get charged for it.
So annoying

I received 2 calls from this number this evening trying to sell me Vonage VoIP services.

After transferring me to a supervisor because they could not accept I already get services cheaper than they provide, he hung up, twice, as it appears he did not believe me.

Didn't have chance to find out how they knew my number

ththis number keeps calling me at odd times, of day and night, only rings a couple of times, but allways to my mobile

havent managed to speak to them yet, when i call the number it says it doesnt accept incomig calls

Had a call from this number. I picked up but they hang up. tried to call my service provider and they advised me to contact the police.