If I put my mobile phone in my microwave oven and close its door, Should I be able to get incoming calls ? Because, I tried it and I was able to get calls, what does it mean? Does my microwave oven has a radiation leak?
No, your oven does not have a dangerous leak. It is designed to only contain only the frequency used by the magnetron (2.45 GHz). The frequency bands used by cell phones are very different.
In particular, the door "seals" are rather frequency-selective. Instead of trying to maintain a good electrical contact between the door and the rest of the oven box, they are designed as quarter-wave waveguide "traps" that prevent the microwave energy from getting past them. They have little to no effect on cellphone signals.
See Skeptics.SE for additional details.