Actually Mel, the Direct Debit guarantee states that any problems with a DD should be credited back to the persons account and disputed from there. Also any charges incurred due to the DD should be refunded and only recharged if the original DD proved to be correct. The originator MUST inform the account holder of any changes to the amount being collected in advance of the collection date
Full details here
http://www.bacs.co.uk/BPSL/directdeb...ic/yourrights/
BTW, my mum got hers last week as well.