Daytime calls are also set to be increased from 3.25 pence to four pence per minute at the start of April, while the price of line rental is rising for the first time in two years by 75 pence.
Commenting on the changes, Gavin Patterson, the BT Group managing director, said: "Weekend calls are being given away for free to millions of people and there's the added bonus of free evening calls if customers take a contract and stay with BT."
BT is one of the world's biggest communications solutions providers, operating telephone and internet services in around 170 countries.
The company recently unveiled a new range of energy efficient phones for homeowners looking to improve their green credentials.
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