Vodafone

It follows an earlier investigation that found Vodafone had misled pay-as-you-go customers over top-up payments.

The regulator also said Vodafone had broken the rules on handling customer complaints.

Vodafone offered its "profound apologies" for the failures.

The fines stem from two investigations into Vodafone, which has 20 million mobile customers in the UK.

One found that 10,452 pay-as-you-go customers lost out when Vodafone failed to credit their accounts after they paid to top-up their mobile phone credit.

The move means customers will not be billed the current £18 ($23) monthly charge but only if they commit to an 18-month contract.

They will still get a landline connection and phone number, the firm said. Prices will start at £22 a month.

However, some experts said the charge is being merged, rather than abolished.

"To be clear, Vodafone isn't really abolishing line rental charges, it's simply combining the charge into its fibre pricing," said broadband expert Ewan Taylor-Gibson from uSwitch.