Shocking service

A little over a year ago I bought a 3kva inverter with 4 battery system from AC/DC Alberton. I clearly asked if it was upgradable and if another inverter could be added to it if ever I wanted to increase the size of the system. The manager there assured me it was as long as I use the same 3kva inverter. 22k later I went home with the system. Now I wanted to add a second system and was assured the same from same manager only to be told by Ryan from HQ that this is not the case and that they are not able to be put in parallel and that only 5kva inverters have the capability. He said he would investigate the matter and call me back. Well over a week has gone by and still me feed back from him or store.