Check with your provider for their program. If you have your phone on, it will receive calls. Some phones, however, will cycle more frequently with this arrangement. Cycles on batteries effectively shorten the life of your battery. Check with your phone manufacturer for details.
Some phones have a toggle arrangement on the side of the phone.
There are other models that require you to go into the menu settings. Refer to your owner's manual for your particular model. You may also be able to ask your providers customer care representative. In most cases, you will have to go to the phone's menu program to make this adjustment. Many models also allow the ringer to be completely turned off.