Bad service after purchase

I recently purchased a Totem XC330 bicycle (27-04-2018) and when I assembled it and took it for a test drive, the gears kept on slipping and didn't function correctly.

Upon me phoning the game store (04-05-2018) the reception lady that answered the phone directed my call to customer service which didn't go through as they were probably busy. I tried phoning 3 times after my line got dropped and on the 3rd time I got through a lady in customer services named Thato answered the phone sounding half asleep not really feel like assisting.

I feel that as a customer the lack of professionalism or efficiency should be handled better.