Awful experience

I bought a gas heater online at Makro then I returned it back as it had a defect. This was on 1 March. I was then promised that a new heater will be returned to me on 12 March. I have waited and called Makro numerous times but with no luck. I have requested for a refunded and I'm told they are busy with. I am the one who has been calling Makro almost everyday and i have been getting no correspondence.

I want a refund immediately and I'm quite exhausted by this awful experience.