I know someone who called retentions about leaving and going to BT. they were offered a cut down price of £18 a month if they stayed with VM.
she was waiting for the confirmation of the £18 in a letter (because we all know that they deny the offer was ever given)
no confirmation letter emerged. so she called back to ask for it again. they said they had sent it out but would send it again.
"but the offer he gave you of £18 was wrong. it's actually £25"
she told them to stick it.
they always do this. pluck a price out of the air and deny ever giving it you