assistance with home loan

I am a young professional and I'm planning on buying a house, earn well enough to pay off the home loan and have a permanent job. However, I do not have a credit rating as I have no credit. The bank has approved 70% of the purchase price. I need a 100% loan and am a first time homebuyer.I have to go through FNB as I bank with them and they are they consider a cheque account as a credit card. Can someone who works at home loans please assist in helping me motivate for a 100% bond? Or any other helpful advice would be apprreciated