Shame on M Web

On 13/2 my new M Web modem was delivered. On Monday 16/2 I purchased 2 FON WiFi range extenders from M Web in Canal Walk, and was informed that, should there be a problem with the product, I may return it for a new one on condition that it is within one week from purchase date. I was also informed that it is a plug-and-play product, but was told that I can contact support, should I have a problem with the programming. I called support on Monday evening around 6h30 because I experienced problems with programming. The light on the extender was not stable, it was flikkering all the time. I was infomed by support that there is a problem with the heart beat of the modem and that some of the modems have this problem. I was given a reference no *** and told that they will attend to the matter. She could not say whether it will take hours,weeks or years. Since Monday I have been calling every day, only to be told they are looking into the matter. Friday 20/2 will be a week since I received the modem and if there is a problem with the heart beat, why don't they exchange the modem?Monday is the last day to return the Fon extenders, and I am still unsure whether they work.