Unsuccessful Mandate

Hi I am an ESL teacher. I teach for a company in China and I’m required to sign a mandate. It bounced back saying: Unsuccessful mandate”.. perhaps I made an error- not sure. All I know is that I have been i trying repeatedly via email, telephone calls to reach the mandate department- with no response at all!!All I need, apparently, to be able to withdraw my funds from Payoneer, is a new mandate! Why is this so difficult?? I’m appalled at the service rendered or in this case, not rendered!