Pick n Pay poor customer service

Hello Peter I recently bought a bmx bicycle at Pick n Pay Hyper in Ottery at R1000 for my 8 year old son,the following day the bolt that holds the handlebar together was warn out.So I took it back that same day with all my receipts and the box that the bike was in.The sales person offered to replace the bolt,but failed to find a similar one.this is when I insisted that they give me a new bicycle.the bike work fine for Two weeks then the welding on the handlebar’s neck came lose...now I live in Athlone and that a 20 drive away from ottery.so needless to say I went back and asked for a refund,instead the manager Mr Granger gave me all sorts of reason why I can not be refunded,told me that the distributor needs to asses the damage,and that they would call me the following Monday,today the bycucle was delivered and I could see that it was just quickly fixed,after a few minutes of riding his bike my son came back and said that the handlebar is loose again. Pls tell me what to do. Sincerely Dissatisfied customer.