Dissappointing Product bought

On the 16 Dec 2015 I bought 2 bikes for my 2 boys, each costing me R800. I got home, the bikes were assembled and one of the bikes tyres had to be bumped at the garage. with in an hour of my husband pumping the bike, before my son even rode it the bike was flat again. My son had to go to the garage and pump the bike and only then he could ride. The next morning the bike was flat again, seemingly every single time my son needs to ride the bike he has to pump it a number of times a day. I called Makro Alberton and I spoke to a gentlemen as Sports Dept who was totally useless and he informed me they don't give any guarantees on bikes. I demanded to speak to his Manager, she also informed me there is no guarantee that my son hasnot gotten punctures while riding the bike. The lady was really rude and after spending R1600 on these bikes, I deserve better treatment from the staff. As of today I am sitting with a bike that cannot work and is still in mint condition. But due to lack of service from this store I am really stuck and out of ideas.