You migrated on 21 Jan, but when did you give BT notice you were leaving? Asking for a MAC is not giving notice cuz you don't have to use it.
Did you use MAC to migrate?
It looks like BT has taken your call of 6 March as terminating the contract.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC