I called back number (02) 8246 7029 spoke to a woman who said company name is rail tram and bus union.

I took a call from this number saying it was from UNHCR, the refugee support organisation I support. The caller was asking me to increase the amount I pay each month. I politely refused and ended the call. I then looked the number up and it came up as being a Title Trade Mark organisation.

Caller: Mondial

Missed a call from this number, Google search revealed Title Trade Marks Law Firm. Called the number and it was Mondial, who operate a call centre on behalf of charities.

Missed call on my work phone, left a voice message of just heavy breathing

Missed call from I think the person was saying monditow or something

Yes, I too have supported UNHCR in the past and and got this call today, though I hung up before they spoke as I was working

I answered this call and got total silence! Blocked now.

Did not leave a message and my phone has registered it as a call from "Title Trade Marks", most likely spam/scam call