The Simple tariff offered customers up to two Sims with 50 minutes and 50 texts for £6 a month with the first two months free.
Carphone staff admitted that many customers exploited the tariff's 30 day cancellation period by ending their contracts in the first two months before they had paid anything.
A Carphone spokesman said: ‘We have been delighted with the success of Talk Mobile Simple, which has clearly appealed to a broad base of customers.
‘However, as with any other network, we continually modify and adapt our tariffs in order to meet the evolving needs of our customers.
‘We are committed to Sim only tariffs and will be introducing a new set of Talk Mobile Simple tariffs in April.'