The number you have is a US toll free number. These are issued at a national level so there’s no area code. The USA’s country code is 1 so, to dial the number from Australia, you should enter the following: 0011 1 888-688-4760.
Note that toll free numbers are designed to be dialed nationally, therefore calling this number from outside the US might not work. If this is the case try the link below where the business you have been trying to contact provides additional regular contact numbers from their Canadian office (Canada uses country code 1 as well).
Just wanted to say how much I appreciated your answer. I was on to Telstra for a long time asking if they still had the enquiries number 1225 (for international) and they didn’t know. Typical Telstra service I’m afraid. Thank you for the quick reply. I realise there may be a fee but that’s OK as long as I can reach them. Again thank you.