What to think about my boyfriend being called twice in the evening by a girl who told him she loves him?

We were at my place and he got a cal from this girl who told two months ago she was in love with him but he didnt respond to that. She showed me all of theiir messages and the last ones were in september but now i am doubtful because he says that he dont talk to her at all but i am not sure. She left him 5 vocal messages.. But he says he can do nothing about and it is not his fault. Now I dont know what to think about it?