Subsequent notices of arrears issued on credit card debt by Assignee

[margaret123]

Hi, Im dealing with a county court claim re: credit card debt on behalf of my sister, and she has been sent subsequent notices of arrears every six months from the Assignee of the debt which state they are sent in compliance with the CCA 1974. I cannot find which provision in the CCA states that subsequent NOSIAS must be sent every six months under a credit card agreement; section 86B states this is the case for a fixed sum agreement, does the Assignee of a credit card debt have a legal duty to send a subsequent NOSIA every six months in the prescribed form? I would really appreciate some advice on this, thank you