Pensioner totally ********** with heavy overcharge for geyser replacement

Total rip-off for replacing a 200l geyser - charging R17,800 for a R12,000 job. Desperate pensioner forced to pay cash for the job. Insurance only paying +-R10,500 less excess means receiving just about half of that cost. To top it off, replaced Kwikot geyser with another brand - unknown to insurer. Please note I am lodging this complaint as Chairperson of the Body Corporate of the complex in which this work was done. I did phone the HO but they want me to speak to the technician, which I feel is not up to me to do. The pensioner is too stressed to follow this through.