The first thing you should check whether your iPhone is loading the correct Carrier Budle after unlock. For this purpose, go to Settings->General->About. If it is showing the irrelevant carrier budle, this is you main problem which is preventing the activation of FaceTime too.
Follow these simple steps to resolve the No Cellular Data and FaceTime Issue.
Step 1: Launch Cydia and add the following source cydia.pushfix.info.
Step 2: Install Carrier Reset Fix.
Step 3: After the installation is complete, remove the SIM and reinsert it.
Step 4: Go to Settings – General – About and now you will see the correct settings.
Step 5: Slide ON the FaceTime in Settings and it will start working again.