Kent RO — Unit not working and technician not attending

I have purchased Kent RO in 2013 in visakhapatnam Andhra Pradesh. From then on some problem or the other. We have to keep on calling the technicians but they won't respond. They simply give us complaint number but won't attend. In 2014 Nov we faced problem and got the unit repaired by spending around 1500. Again in the month of April 2015 we faced the same problem (water not coming). We have spent 2850 to change RO. Again on 1-5-2015 we had prob. After calling repeatedly techi attended on 13th. We have spent 885/-. After two days again problem started and machine is out of order. It's been four days we are requesting the technician to come. He is saying today evening, tomorrow morning I will come but not coming. Not lifting the calls also. I want to know the exact service centre in visakhapatnam where some good technicians are available and who can actually find out the problem instead of guess work and wasting our money and time. Very pitty to say that this product is the worst I have ever used. after sales service of this company is the worst I have ever seen. Even small companies they are trying to give the best service but yours is really worst. Kindly guide me how to fix this.