Breach of Contract & Professional Negligence

First of all we paid R16000 which is 50% of the job to be completed for a gate and wall, so they sent us a quote stating the job would be complete in 5 days. 5wks later we cancelled the gate as they hadn't even started the installation, now we on on our 6 week and they still have not completed the wall which in the total quote was only R10000 out of the R16000 i paid and they are completely avoiding me, so I'm prepared to write the other R6000 off as bad debt and recommend no one ever use them, i would have at least expected for the money i have paid that our wall would be finished without all the cracks in the wall. Its breach of contract and professional negligence