May paid Hidden Hearing, based in Maidstone, Kent, £974. But then her device had battery problems and was taken away for repair.When it was returned, the 79-year-old found her hearing little improved.

Despite being over the 30-day legal limit for returns, May, from Melksham, Wiltshire, asked for a refund. Initially the company refused but then had a change of heart. But to May's dismay it still kept £150 of her money.

"They say it is for a professional fee, whatever that is, but I can ill afford to lose that much, " she told Crusader.

"The fee was for home fitting and administration, " explained Richard Geldard, Hidden Hearing's customer service manager. However, he has now returned the full amount.

"Holding back £150 in these circumstances seems normal but we'd like itemised billing to become standard so people know what they are paying for, " said a spokeswoman for RNID, the national charity for the deaf and hard of hearing.

The Hearing Aid Council regulates private dispensers and the RNID's website carries information about hearing aids: see www. rnid. org. uk or call 0808 808 0123 for details.