The South African Post Office, which has taken over disbursement of social grants to poor South Africans, has urged recipients still using old South African Social Security Agency (Sassa) cards to trade them in for new ones before they expire on December 31.

It said Sassa would not be able to deposit any payments for January into the old cards.

"According to Sassa, there are approximately 500 000 Sassa beneficiaries nationally who have not yet switched to the new gold Sassa card," the Post Office said.

The new cards can be collected from Post Office branches and Sassa offices nationwide.

They offer one free cash withdrawal per month over a Post Office counter and unlimited free swipes at all retailers to pay for purchases.

The Post Office said its partnership with Sassa had freed millions of social grants beneficiaries from unauthorised and unwanted deductions from their new cards.