Elizabeth,you describe this as a regular monthly payment in which case it is highly unlikely that it has suddenly gone to another person's account. Sadly it would appear that you are being misled. A word with your bank may help to clarify the situation.
It's what I think too and very odd that it has been regular for the last 5 months but suddenly it went astray. I believe they are simply trying to put off paying what they owe due to Christmas, but they seem to forget it's Christmas for me too.
Will have to wait now for a few days before I can really investigate and get what I'm owed.