A Surrey man is questioning the tolling system on the Port Mann Bridge, after he was billed for six trips he did not make.

Dave Stewart, a former police officer, was charged for trips made by drivers of Quebec and Washington vehicles with the same numbers and letters as his B.C. plates.

"If you have an account with TReO and another car from another state or province crosses that bridge with your plate, you're being billed for it," said Stewart.

A customer service representative with the Transportation Investment Corporation — the B.C. Crown corporation that runs the Port Mann Bridge — admitted that licence plate mix-ups happen.

"[It’s] a coincidence that it's a plate with similar numbers or the same numbers, but it still happens from time to time," he told Stewart by phone.

TReO has issued Stewart an apology and a refund. He has also been registered for a tolling decal which should differentiate between B.C. plates and plates from other places.

But he questions how many other motorists are being charged incorrectly without their knowledge.

"If it's happened to me, it's happened to hundreds of other people for sure," Stewart said, adding that the information is shared with ICBC.

"When you go to renew your plate or your licence, they're going to want what TReO says you owe them before they renew," he said.

The Transportation Investment Corporation maintains that its toll system is accurate, but admits mistakes can happen when there are three million crossings a month.

Last year, the corporation sent letters to hundreds of newly-registered bridge users over fears their accounts might have been compromised by a rogue employee.

With files from the CBC’s Belle Puri