Have you tried restarting your phone?

Does texting and/or cellular data work? Or can people still call you?

Does your phone show that it has service?

Hi I tried everything it was OK before but now I cannot make calls or receive calls. I asked koodo chat and they scheduled 3 times since yesterday at first I am able to talk to them but then suddenly call drops and when they try to call me I am unable to answer the call . I am very upset as I pay my bills on time and I should not get this kind of service please solve the issue. 

Hi I don't know where to contact koodo trouble shooting dept as you guys do not have proper chat where you can talk to the csr or tech who can help to resolve the issue. 

I interpret that as you have tried to restart your phone.

Have you tried resetting your network settings on your phone?

Can you also answer the other questions Allan asked?

Yes text message , and data works but phone calls I cannot make it and calls I receive only stay for few minutes then disconnect or drop calls.

Are you able to dial out when you insert your SIM card into another device? How is the signal in your area? If you have an Internet connection, have you tried setting up wifi calling?

Yes I tried resetting network too but no use

EDIT: Thank you.

Next step is to try what MilkyWay suggested above.

It will determine if the issue follows your device or your sim card.  You can also try a working sim  card from a friend or family in your phone to see if the problem occurs