Keeps calling. Annoyingly persistent

Did not pick up the call. I make it a point to pick up only from numbers I know or are on my phone. Too many time wasters.

Scam

Difficult to understand accent but seemed to be about government energy efficient programs.

Three calls within one day. Called back on a withheld number and there was a voicemail system but I couldn't understand/hear who the call was from. Seems to be a call centre of some sort, with a pause, then a beep before the call connects. Always a dead giveaway so gives time for a quick hangup