The investigation by regulator Ofcom found that Plusnet broke a billing rule by continuing to charge a group of customers for landlines or broadband after they had cancelled their service, the regulator said.

Ofcom said that the 1,025 customers were overcharged by more than £500,000 in total.

Plusnet, which provides broadband, landline, digital TV and mobile services, has refunded 356 customers a total of £212,140, which included interest at a rate of 4 percent for each customer, Ofcom said.

Plusnet has also made clear to Ofcom the action it has taken to prevent any future billing errors of this kind.

($1 = 0.8025 pounds)

(Reporting by Arathy S Nair in Bengaluru. Editing by Jane Merriman)