Return broken cordless drill: no response from the company

I have ordered for sometimes from them and everything was always received in good order and according to their delivery notes. Now for the first time i'm having a problem with the last product that i received. I have ordered the 20W cordless drill set which again was received in good order. Then i used it once and something went wrong inside an the chuck is not turning as soon as pressure is app**** to it. I have send them a whattsapp already on the 14 August and i was asked to send them a video. Then i was shown the direction button and I explained to them that its all working fine and that is not the problem. The problem is inside the gears. Ever since no response from them on their whattsapp. I have also tried to call the whattsapp no and also no success. Seems like once you order from them all is good but on the return side its very difficult. All i want is a replacement for a broken cordless drill and answer if i lay a complainant. Why then the whattsapp number if there is no response?Hope someone out there can give me some guidance in how to solve this matter