The press ad read, "Smile. Talk is cheaper with NTL. With so many savings you can use the phone more."
BT complained that the ad misled consumers in the belief that they could save on all calls through NTL.
The Advertising Standards Association ruled that NTL should not claim that customers can make total savings on services if a competitor's rates were at any time cheaper than their own.
NTL promised to withdraw the ad, which it said was a one-off, and was told that ads making similar claims should be vetted by the watchdog in future.
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