I recently had my phone unlocked, and I was wondering if there is a way to tell if it was done successfully
You can check it in Options/Advanced Options/SIM card and then type the letters "mepd" and it will say Inactive or Disabled.
Or
You can also pop in another SIM card and go to Options/Mobile Network and change Technology to GSM/UMTS and select 2G and see if the phone reads the SIM