Johannesburg's billing problems, which have resulted in residents receiving inflated bills and others having services cut off, are not a sign of a crisis, says mayor Amos Masondo.

He attributed the problems to the implementation of a new IT project, Phakama, designed to improve the city's billing system.

"We empathise with residents currently experiencing difficulty and will ensure that the numbers affected are as minimal as possible," he told reporters in Braamfontein.

Masondo said the number of people owed refunds was no longer a "big issue" as it had been reduced.

The city's head of finance, Parks Tau, said implementation of the IT project had been completed and that problems with it were "interface-related".

Asked about the inflated bills, Tau explained the billing process in detail, said they should not have been issued and that investigations were under way to hold those responsible accountable.

Tau said the city was owed about R10-billion and credit control processes were under way to collect the money.