Meccer 5w Inverter and the service Mustek very very disappointing and worst customer service

Purchased a Mercer 5KW Inverter controller from FNB TECH two weeks ago, This was purchased through my electrician a qualified installer. From day 0ne there were problems with the inverter came as a code 8 error , He took it to Mustek at Nandi Drive Durban they said the firm ware needs to be upgraded which they did and never tested the inverter on site. The inverter was re -installed this time the unit was clicking and again gives a code 8 error, The electrician contacted Mustek again , he was told to bring the inverter back again for them to check which will take another 5 days. I requested the electrician to asked the supplier for a new unit still waiting. for a response form First Technologies. Its one of the worst experience MECCER BRAND IS LOT to think about . Why was this inverter not tested and checked by Mustek. Everytime my installer checks on the progress of the inverter from Mustek they do not give him a definite answer