Perhaps you should look it up.
Microwave ovens don't cause cancer. It was once claimed they did, but further studies have shown that they do not increase the risk.
Similarly, it has been claimed that cell phones cause brain cancer. This one is more complicated, because cell phones have only been widely used in the past 10 - 15 years, so long term effects cannot yet be known. A few years ago some small studies suggested a link between cell phone usage and cancer, but this has since been dismissed by further, larger scale studies. Any risk if present is likely to be small.
So you cannot compare these examples to sunbed use, where there is clear evidence for a significantly increased risk of skin cancer as a result of usage.