Almost 30,000 people got a surprise text message from the Ministry of Justice on Monday telling them to urgently get in contact.
The ministry says it sent out messages to 29,600 people with outstanding fines, asking them to call an 0800 number to pay them.
But it says through human error, some people who had already paid their fines were also texted.
A spokesperson says they have sent out a second text, telling those people who have no outstanding fine to disregard the message.
The call centre was jammed with extra calls this morning, and ministry staff say there were delays of about 20 minutes a call.