Aastra 480iCT call waiting

Having problems with AASTRA 480iCT and call waiting *70.
When I dial *70, Freepbx says it’s enabled.
When I dial the 480iCT, while it is on a call I get a busy from FreePbx.

*70, call waiting works properly on the same server with an AASTRA 9133i and works with the LinkSYS ATA.

Anyone else with this problem?

James Taylor