If you need to make a phone call and the iOS 8.0.1 update broke your phone leaving you with no cell service you can still use the iPhone as a phone.
You can make a phone call over WiFi using the iPhone on iOS 8.0.1. You need to connect to a WiFi network at home or a free public WiFi network.
If you need to call another iPhone you can use FaceTime Audio, which is a voice only FaceTime call. This works on WiFi to another iPhone or to an iPad.
Another option is to use an app like Google Hangouts to make a phone call. Many Gmail users already have the ability to make a phone call from the Hangouts iPhone app. This lets you make a free call to any phone number.
Other people can call you on FaceTime Audio or of your Google Voice number is linked to Hangouts, but calls to your regular number will not work.
To make a call over WiFi on iOS 8.0.1 you can use FaceTime Audio. Open the contacts app, find the contact you want to call, tap on the contact and then on the FaceTime line tap on the phone icon.
You can find more detailed instructions on how to make a FaceTime Audio call on iOS 8. remember you need to connect to WiFi first.
A second option is to download Google Hangouts free from the App Store. Sign in with your Google ID and password and when prompted link your account. Tap on the Calls option in the lower right. Now you can dial any number you want. If this is the first time using it, you need to allow access to the camera and microphone.
Here’s more on making a call with Google Hangouts from iPhone.
These two options will allow you to keep in communication until Apple releases an iOS 8.0.2 update to fix this problem.