Hi ive had a letter come through this morning from the job centre plus?

Someone has obviously told them that your boyfriend is staying with you, or lied to say that you are working. It is also possible that the jobcentre plus has had an investigator watching you. The phone account might be a bit tricky, but all you can do is explain the situation to them. Just tell them the truth, as it doesn't look as though you have anything to hide.