Ughhhh

so I’m 17, and my boyfriend has gone on holiday with his family for 2 weeks. His nan lives with him and his mum. I said I’d go and see her at some point so she wasn’t on her own she she’ll have some company. I couldn’t go in the first week which was last week I told my boyfriend and he failed to tell his parents. I have gone to see her the second week which is today, but his parents are really annoyed at me?! I was never given a day to go they just asked me to go and see her?! Have I done anything wrong? The first week I had my own family commitments to take care of that I couldn’t get out of.. what do I do to make them not hate me🙁