Ducing Call Unblock Unblock blocked calls and much more. Call Unblock allows you to see who is calling even when the caller has blocked their caller ID. NOTES: o Supported Carriers: Sprint, AT&T, TMobile, and Verizon. O Pay As You Go and Pre-Paid phone plans are not supported. O The app is not free. You must sign up to a monthly or yearly subscription to use the service.