Poor & unprofessional service, change quoted price

On the 19/08 I accepted a quote from the above company and paid a 75% deposit for the installation of a new geyser including vacuum breakers, tray, copper pipe and fittings.The price included the call out fee and service of my current heat pump with the installation of a banjo valve, loading valve and loop, on the written quote. The company's installers arrived at my house on the 21/08 in a sedan, without any step ladders or other means of getting onto the roof to do the work. They took 2.5 days to do the installation, but could not get anything to work. Sheldon came out to check and told me he thinks that the return pump was not working and will came back on the 24/08 to swap out the pump= he never came,he made another appointment to come on the 27/08= he never came, new appointment for 28/08 also no show. on the 29/08 the installers came back again without a means of getting on the roof. In an attempt to do fault finding they disconnected the new geyser and cut off all pipes leading to it, they got the heat pump to heating up +/-10L of water only from a 150L geyser. On the 03/09 Sheldon informed me that I must pay an extra R2047.96 for the work, I still dont have hot water