I'm sorry that took so long, I wanted to make sure I give you the right answers to suit your needs.
Okay so usually disputes with insurers can be referred to the Financial Ombudsman Service. But you need to ensure that the insurer is a member. So check here to make sure they are. I've checked Suncorp at that link and there are a few entities that come up with that name so best if you check your policy to see which entity you contracted with and see if it comes up. The steps for making a claim through the Financial Ombudsman Service are here. Make sure you check the steps you must take before you lodge, which you will find here. Sometimes you might find you need to pay for the repairs before you can be compensated - this will certainly be true for the next option we shall discuss. A quick call to the FOS to ask should clarify this (I can't call now, phone lines are closed).
However with the FOS, you may not achieve a binding result - it depends on what you are seeking. Be sure to go through the Insurance Contracts Act to find out what you think the insurer has breached. I can't advise you of this as I haven't got your policy. The Act is here.
Another way around it is you can just sue them for breach of contract in a Court of law. The Magistrates Court of Queensland would be the one to sue in for this type of claim. You will probably need a lawyer to draft your statement of claim but you can give it a go yourself if you wish. It will be for breach of the term giving the guarantee if you can find it in the policy and reference it. Or there may be another term breached. Perhaps a term about quality of repairs or repair service. Have a look through the policy. The Magistrates Court webpage has a section on how to represent yourself in Court, so work through that. You'll find the webpage here. It costs money to lodge a claim in a Court but the result is binding on both parties. If you lose, you may have to pay their costs, that is the risk you take.
If you want to save money on legal fees, you can try and find the local law bookshop and buy a simple text on contract law, it should cost under $100. Or sometimes the fees are fixed for small claims, so in NSW for example it costs a little over $600 to get someone to lodge your small claim.
I hope that has helped. If you are happy with this service, please rate my answer highly. Best of luck.