Mr Green, who has operated a $20 a month mobile Telstra plan for a number of years, has been left incensed after being told his plan would automatically rise to $30 a month as of November.

“There was no correspondence whether I wanted it at all,” he said.

“We received a letter with our latest bill that said the increase would automatically be applied to our plan,” he said.

“It’s a 50 per cent increase. How can they do this without even telling us?”

Mr Green and his wife don’t use the mobile as their main phone.

“It is mainly for emergencies or if one of us is in town and we need to contact each other,” he said.

“We very seldom go over our $20 a month limit. We have only gone over four times in the past 12 months.

“Then all of a sudden they are going to lump us with an additional $10 a month charge.

“There will be an awful lot of people, including pensioners like us, who won’t be able to afford it.”

He rang Telstra and was told the Australian Competition and Consumer Commission said the company was within its rights to increase the charges.

“I was cheesed off. I was even more cheesed off by the arrogant, high-handed attitude of the call assistant who said ‘they were allowed to do it, so they were are going to.’” he said.

“I was told alternately, I could cancel my contract and have my connection cut off or look elsewhere.”

A Telstra spokesperson said the way its customers now use their mobile phones had changed.

“Customers who had changes to their plans will also receive unlimited eligible calls, SMS and MMS to use in Australia as an additional inclusion on their plan,”  the spokesperson said.

“We are providing our customers with more value on these updated plans to help them get more from their service.”

He said customers on plans who were ‘out of contract’ could choose to change their plans whenever they like to find the best value one for their needs. Customers currently in-contract have the freedom to cancel or change their plan without incurring any early termination charges to find the best plan for their particular needs.

“We understand there’s never a good time to change prices but this is the first time the price of these plans have changed since these older plans were first introduced, some of which are more than 10 years old.”