Hi @shane_24 ,
You could try [https://www.hardreset.info/devices/blu/blu-studio-70-lte/recovery-mode/|wiping the cache partition] in the phone and check if this resolves the problem.
'''Do not select wipe data/factory reset''' ''as this will erase all your data and downloaded apps.''
Also try starting the phone in [http://howtosafemode.com/2784/how-to-turn-on-safe-mode-on-blu-studio-7-0|safe mode] and check if an ordinary call works OK.
If it does then a ''downloaded app'' is the cause of the problem. The trick is to find out which one. You’ll need to uninstall each ''downloaded'' app, one by one, and test the phone in normal mode between each uninstall until it works OK. When it does then the last downloaded app that was uninstalled was the culprit.