Hi Techeis11,
Welcome to the Apple Support Communities. Voicemail is definitely important! As we understand it, you installed and then uninstalled a call blocking app and have found since then that you're not receiving voicemail. Is that right?
For clarification, do you know what's happening when someone calls you? Does it ring and not go to voicemail, or are they leaving voicemail but you don't receive them?
This link has some great steps regarding Visual Voicemail: Set up Visual Voicemail on your iPhone. We recommend reviewing the "Get help with Visual Voicemail" section to see if that helps. If the issue persists, we recommend getting in contact with your wireless carrier next, as they're going to be in the best position to assist with voicemail issues.
Cheers.