Go to iPhone Repair and Service - Apple Support
Go down to the estimate tool and selected the service for the rear camera. I do not see a listing for the iPhone 11 but it may be because Apple changed its web pages not long ago and several of its features no longer work with my browser. If you also do not see it:
Refer to this page for Apple Support features ➔ Contact - Official Apple Support
Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that offers a chat session or a telephone call and get the representative to redirect you.
This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple for support and service - Apple Support For some countries look under “Other” listing at the end of each region. Not every country has telephone support.