The Independent Manchester United Supporters Association claim to have been besieged by irate supporters who have had a £23 subscription for the Red Devils' 'One United' membership scheme taken out of their bank accounts despite telling the club they were no longer interested in the service.
One fan even claimed a new direct debit had been set up without her knowledge to replace the one she had already cancelled, which then took the annual payment.
United officials do not believe any fan who wrote directly to the club before the 14 June cut-off date has had money taken out of their account but it is undoubtedly an unwanted row on the eve of the Old Trafford outfit reverting to Malcolm Glazer's ownership.
"Anyone who has had money taken out of their account but does not want to be part of the One United scheme should write to us," said United communications chief Phil Townsend.
Cancellation of membership schemes is part of the concerted campaign by sections of the United support to wreck Glazer's business plan.
IMUSA and fellow fans' group Shareholders United believe a boycott of club merchandise will destabilise Glazer's long-term strategy for the Red Devils and eventually force the Tampa Bay Buccaneers owner out.
Last week, United reported record season ticket sales, yet even those figures have been ridiculed by IMUSA campaigners, who are adamant the effect of their actions is starting to bite.
"It is becoming clear to us that although the club have released so-called increased ticket sales they are actually hawking them round to anyone who will have them," claimed IMUSA chairman Mark Longden.
"Two years ago, United were the hottest ticket in town, now the club are looking like the Del Boys of the North-West.
"We would urge every fan to look closely at their bank statements and then make sure they get their money back."