Four retailers have contacted me over the past year to relate their dealings with a company called SD Media, which puts together ads to run in post offices, doctors surgeries and so on. In all four cases the retailers claim that the rep had signed them up for a trial period at about £100 but then had filled in direct debits for two more payments ranging from £500 to £900. 

In the case of John Clark from Express Stores in Margate, there was nothing in the account to take. In the other three cases - Subhas Patel from Spar in Richmond, Andrew Hutchinson in Plymouth and Tony Ducker who runs Fen Park Stores in Stoke-on-Trent - each retailer stopped the second direct debit the minute they spotted the first one. They have now all been threatened with court proceedings.

All four also claim that they cannot find their ads in the locations that have been specified.

I contacted SD Media and the spokesman said: "With our contracts the terms are explained across the centre - how much the deposit is and how much is still due. It is crystal clear. They pay a deposit and then the rest is split into two payments. We guarantee the locations and have a few thousand customers."

Subhas thinks that there may be strength in numbers and asks if other retailers who felt they were misled will contact him to see if there can be any recourse. His telephone number is 020 8940 0803.