Hi there,
Welcome to Freelancer.com
I am experienced iOS developer, i can develop Church SignIn App in quick turnaround and exactly within your budget. It's all up-to me for handling backend to store User's phone numbers, do you have Hosting Server? No Problem for initial stages i'll use mine, but you should have for future perspective.
Do you have apple developer account? If No, i can offer you 1 year universal installation of app to unlimited devices.
If you want to submit to apple store, i can help you with that too.
Looking forward for productive discussion.
Regards,
Farooq