How to move SIP devices to other Tenant ?

Hi,

I tried setting up SIP device in A tenant's SIP gateway and it worked. Now for some reason, I need to move the SIP device to B tenant. Before deleteing the mcaddress, I already made sure the device was signed out from the previous pairing. When the 'Sign-in' showed on the screen, I deleted the mcaddress from TAC, but not sure how to unenroll this device from *55* dial before. Next I reset the device to factory setting. 

When I provisioned the device to the B tenant, I noticed that the device show 'Sign-in' screen as if it's already enrolled before. When trying to pair with user in B tenant, it failed to get the account. Looks like it is still connected to the previous tenant. 

How do I remove this device completely from previous tenant? 

Since those tenants share the same provisioning server, is there a waiting time for the server to completely remove the mac address from its cache? 

Thanks in advance