unstable connection

Hi! after 6 month strugling with my  EX3110 wlan extender, I come to the point to claim for refund  because I did many things to solve the problem of unstable connection and still I had to restart the extender many times per week, I have tried many solutions such as : static ip address , 2,4/5 GHz, new software updates  and so on(totally I spend more than 10 hours on this extender during last 6 months and still suffering poor connection) . please help me about the issue !

how can I claim for Refund?