Telstra has come under fire over its revamped email service with customers complaining they have been left without access to their accounts for days.

Despite promises customers could expect a “simple process” to access a “new improved email service”, business owners who rely on their accounts for work have told The New Daily Telstra Mail has proved a “nightmare”.

One customer, who did not want to be named while Telstra dealt with the problem, said he had been unable to send emails for more than three months.

“I was reassured when they went over to Telstra Mail that I wouldn’t even notice,” the customer said.

“The moment they changed I couldn’t send through my Bigpond account.

“I’ve now spent over three-and-half-months making seven phone calls, which have gone for over an hour. At the end they’ve said, ‘Sorry, I can’t fix it for you’.

“I run a whole business off my email. It’s the same account I’ve had for 22 years.

“When you’re overseas and WiFi is dodgy, you need to be able to use your webmail. When I was overseas, it was an absolute nightmare.”

The company has been migrating thousands of accounts over to the Telstra Mail service after it was launched in May.

Sydney resident Adrian Downey said he and his wife had been Telstra customers for about 10 years, but had been unable to use her account since it was migrated to Telstra mail.

The account initially worked, Mr Downey said, but has been down since December 30.

“It wouldn’t send or receive. It said it couldn’t locate the server and came up that the account had been suspended,” he said.

Mr Downey said he had contacted Telstra and was passed through a number of different staff members before being told no one could help.

“My wife was annoyed because when we tested it, it said, ’email undeliverable, account does not exist’,” he said.

“It’s her main email address. For example, all of our utility bills, child care and school fees go to this address.

“People she’s provided her email to over 10 years are getting bounce backs.”

In May last year, the company announced Telstra Mail would replace BigPond and Telstra.com mail services.

It said the new service would allow customers to keep their current address while providing added features such as advanced security and increased storage.

“If you have an existing email service with us, it will be a simple process to receive Telstra Mail,” the company said in a blog post spruiking the move.

“We’ll write to you when your service is scheduled to be moved with all the information you need to know and we’ll make the changes overnight to minimise disruption.”

It is not known exactly how many users have been affected, but many have complained to the company on social media and on its customer service message board.

– Four weeks without Emails in October, Now same problem, asked for a Case manager to fix problem, Still waiting for a call.

— Bazza (@BarryAdlam) January 5, 2017

Bigpond mail is now working after 9 days. @Telstra have not called us to apologise or offer compensation for the outage #appalling

— Mark Verbloot (@mverbloot) December 14, 2016

One customer, who has been unable to access emails since January 5, said a Telstra staff member told her the problem was widespread.

“He said, ‘We’re very busy because other customers are having the same problem’,” the customer said.

Another, who relied on her email for freelance work, said she had received a $110 refund off her bill after her email was down for two days in December.

A Telstra spokesman told The New Daily Mr Downey was initially given the wrong information when he contacted Telstra, and it will fix the problem shortly.

“Unfortunately this customer was given the wrong information when they initially contacted Telstra about issues with their email. We will contact the customer today and should have their emails working again shortly. Their issue is not related to the move to Telstra Mail,” the spokesman said.