Hi Leanne,
Generally with unsolicited offers such as this to upgrade your phone plan, you are entitled to a cooling off period during which you can cancel the contract. They likely also would have recorded the call to confirm your agreement to the terms of the plan. Did you receive any sort of confirmation in the mail or an email stating that you have upgraded your plan and advising you of the cooling off period?
With telemarketing slaes, a sales agreement must be provided in writing after the phone call.
The agreement must be written in plain, clear language, be signed by you and the company, it must set out the full terms and conditions of the agreement, including the cooling-off period, state the total price payable or how this will be calculated, as well as any delivery or postal costs, clearly state on the front page that you have the right to terminate the agreement (or cool-off), be accompanied by a form that you can use to cancel the agreement during the cooling-off period and include the seller’s contact details (their physical business address, email and fax number) and Australian Business Number or Australian Company Number.
If you didn't receive this, you may be able to assert that they failed to discharge their duty under consumer protection legislation, which may entitle you to an extended cooling off period of 3 months.
I would speak with the phone company and let them know that you know your rights under Consumer law and state that you believe they have breached their obligations and you are exercising your rights to terminate under an extended cooling off period and see what they say. If you make enough of a song and dance about it and threaten to take it to the ACCC or relevant state ombudsman, they will probably come around. Also, it helps to submit your complaints in writing. Check out the ACCC website on telemarketing sales:
Telemarketing & door-to-door sales | ACCC
