Complaints to Translink have more than doubled since Belfast's new Metro bus system was introduced in February.
The new Metro service is based on 12 corridors
Complaints increased by 107%, with more than 540 complaints received.
Ciaran Rogan of the transport company said while he acknowledged the increase, it had to be taken in context.
"In total we are talking about just over 500 complaints out of six million journeys by bus every month - which is a relatively small number," he said.
"What the figures don't show are the many thousands who are enjoying a better service every day because Metro is bedding in exceptionally well on the ground."
He said he did not want to diminish complaints from travellers.
"We said at the time it was the greatest upheaval in bus services in Greater Belfast in over 30 years.
"So some degree of complaint and comment from those who have had their services reduced is understandable.
"The challenge for us is to address each of those complaints individually - which we are doing - and demonstrate to people that they do have travel options."
The new Metro service is based on 12 corridors along main arterial roads with additional services operating throughout greater Belfast.
Translink has promised buses every five to 10 minutes.
Earlier this week, the cost of Metro and Ulsterbus tickets rose by 2%, while Northern Ireland Railways fares went up by 5%.