The move comes as part of a new flat rate pricing structure for the supermarket chain's mobile phone service.
The Wal-Mart owned group says its new rates are 80% cheaper than Virgin Mobile and its customers will be charged the same rate whatever time of day and whichever UK network they call.
ASDA's Trading Director, Darren Blackhurst said: "We are giving customers the UK's cheapest mobile call plan that's simple to understand and a tariff with no hidden extras".
The new calling tariff takes effect from September 1 and is available to both new and existing customers.
Existing ASDA Mobile customers don't have to do anything to take advantage of the price changes as they will be implemented automatically.
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