Trouble getting a refund or replacement of microwave

We bought a Microwave on January 31 2021. Now in May on the 14th, it stopped heating food up and when it is closed it would stay on even if you haven't pressed anything. We called to say we bringing it in because to me that's a technical issue. Took it back in the box and took the receipt everything they always tell you to keep until the warranty or guarantee has passed. They have the audacity to say they can only see to it Monday. Because the supplier doesn't work weekends. And they have certain processes. My thing is according to the CPA. If the item purchased is faulty within the first 6 months you return it and they refund, replace or repair the item. A repaired item is basically waste of time so the best option is to replace or refund. They don't consider the fact that you must go without a microwave for more than 5 days. It's something you use on the daily. So it's OK for them to violate our rights. But they quick to make sales and reach targets. They have terrible customer service when it comes to complaints. So why did I abide to the rules by keeping the receipt and box for them still to judge me. Cz they assume first that we did something to the microwave.