Go-Ahead has apologised for buses in Dublin either not arriving or turning up late.
However, the company says the latest figures will show complaints have halved.
Stats for April to May found grievances more than doubled on most routes since the company took over last year.
Almost half of the services failed to meet punctuality targets.
Managing Director, Ed Wills, says its constantly improving.
"I think a lot of what we experience, certainly in the stages of our mobilisation, were people contacting us and having concerns about a lot of the times of their buses changing," said Mr Wills.
"We have a lot of comments about the changes to the capacities on the vehicles."