Ppi cmc

clfrey82

Hi I'm hoping someone can give some advice about cmc's.
Back in May my mum filled in an online form with a company called allansons for ppi. About a week or so later a woman claiming to be from a different company magnum claims called her informing her the company had gone bust and details had been passes onto them. My mum gave out her address over the phone and they sent her letters of authority in the post.
At this point she told me about it I thought it was dodgy and told her not to send them back. She didn't.
In late September she received a cheque from black horse for about £1500. She assumed it was just them sorting their own accounts.
Last week a month later she started getting txt messages from a company called HD law saying they'd secured a ppi refund from black horse and someone would call her to take their fee over the phone. We assumed it was the black horse cheque. I obviously told her to ignore until paperwork arrived in post and not to give them bank details over the phone. In the meantime she has been receiving threatening voicemails from the company.
She has now received an invoice saying she owes them almost £600 for a refund of £2500. Which clearly is not that money from black horse. She is going to contact black horse to clarify any claim details.
Is she liable to pay this company when she had not heard of them until the txt message last week, and she did not sign the letter of authority magnum claims sent her as she still has it in her house?
Thanks