Excessive spoofed calls/voicemails to our Auto Receptionist Line

Our organization uses Auto Receptionist to field calls to our staff lines and I recently set up the spam filter last week because we have been receiving an excessive amount (10-20 per day) of calls to our Auto Receptionist main line, which leave voicemails that have a beep at the beginning and then no sound. I've researched some of the phone numbers and it appears that businesses, individuals, and mobile phone numbers are being spoofed. Only a few legitimate calls and voicemails are actually coming through (which is normal) but I have to sort through them to find out which ones are real.