Official complaints about Eir jumped by 62 per cent between July and September compared to same period last year.
ComReg says more than 1,000 were recorded this year, compared to just over 400 in 2019.
Eir is due before the Oireachtas Communications Committee today to address the long wait times many customers have faced during the pandemic.
The company will tell TDs and Senators that waiting times averaged at 30 minutes during the early part of lockdown, but average waiting times are now down to 10 minutes.
The increased number of people working from home has heightened household internet needs and highlighted poor connectivity in some parts of the country.
Sinn Féin TD and committee member, Darren O'Rourke says people are frustrated and angry at Eir's poor customer service.
"We will be looking for clear information from Eir and we also want a clear statement about what they are going to do to address the complaints in the first instance, but also the process for handling the concerns of customers.
"It's completely unsatisfactory that people would be waiting for as long as they are."
