Hitek Security not honoring gaurantee and mis-information when queried.

Bought 13 outdoor vandal proof fingerprint readers from Hitek Security on 28 November 2017. My client complained that 3 units is not working in September 2018. Took it in to Hitek - Justin technician will have a look and come back to me. Week later, still no response, so I phoned in. Spoke to Chantel (manager). She followed up, Justin said the inside of the unit is completely corroded. They do not have any stock to replace them, and anyhow (according to Justin's advice) the same thing will happen again. Chantel agreed to rather refund me. Had to follow up a week later on refund, once I received it I noticed that it is 30% less than what I paid for units. When followed up with Maritsa (Accounts) she said I was charged for 10% handling fee. When I complained that 30% is deducted and not 10 % I had to spoke to owner (Clyde). According to Clyde they only paid out to the value of the remaining gaurantee period (which is 3 years) and which according to him is completely acceptable and their company policy. I feel it is dishonest and they should refund the full amount paid for faulty product still under gaurantee. Be careful when doing business with Hitek Security as this policy is not on their sales orders they send, nor on their invoices or credit notes....