I'm pretty sure your career offers whitelisting. You should ask them. You can block all the incoming calls except for the ones you provide the career with. I know it's probably dozens or even hundreds of numbers, but if you're looking for a permanent solution to your problem, it's worth the effort.
If you choose to go with a silent ringtone, there's also an option to choose 'none' vibration for all incoming calls. (don't unselect vibrate on silent or vibrate on ring. Instead go to settings -> sounds -> ringtone -> vibration and select 'None')
you will have to choose a custom vibration for all your contacts though.
But I don't think it's a great solution, because the calls will still go through, interrupting whatever you'll be doing on your phone.