Very Dissapointed

We Bought an Inverter with 2 x Gel batteries from Z-Tech Computers and after 3 Months, we have problems and took it back, it is 3 weeks later and we battle to answers from them and it is a mission to contact them via telephone, the only way is via email but only excuses all the time about the supplier we are very annoyed and it seems like we have thrown away our money!!!