I’ve been contracted with optus 4 months for my business…

I’ve been contracted with optus 4 months for my business mobile phone plans. When i signed they tell me that they going to send the phone bills to my house. At that time, on my license they still have the previous address, however, i already told them that i changed my address, but they still have to enter the old address in according to their policy. After my bills came via emails, they been contacted me and i said to them that i wanted to changed the address and want the bill to be sent to my house in paper so that i have prove of my address for future reference as well as i would like to know what i being charged for. However, nothing was sent, and i’ve been updated my information 3 times with them. They said the bill will come in 5-7 business days but nothing was received. In the 9 of October they cancelled my bill, i didn’t know because i haven’t activated the sim card that i sign up with them, i’m only using the phone. Then they transferred me to Miltngraham and expected me to pay more than $2000 aud. I refused to pay and call up to explain what happened. After nearly an hour on the phone, they transferred me to speak to a guy in their business plan section. At first he kept sighing which dedicated for very unprofessional service behaviour. I told him what happened, i hold the line for a few minutes then came back with extremely rude attitude even though i was talking very gently. I was angry and told him again that they didn’t follow my enquiry even it was only a simple thing. He said he wasn’t a matter, i still need to pay my bill via my email. I tried to explain but he seems very impatient and keep making pay for the account. Is it my fault and how do i solve this situation because i believe it wasn’t only my responsibility. Thank You