Reinstate contract/ Clear the payment against a bill

Hello Experts,

I am not very well versed with utilities and need to perform the following steps (CRM-IS-U ) :

1. Reinstate XXX contract and cancel with NONE charge – this should reverse the open bill.

2 Need to clear the payment on acct against a bill for YYY Contract so that the contract can be un-lapsed .

YYY is in lapsed state.

XXX is completed ( cancelled by quote )  - XXX is also duplicate of YYY

Could you please suggest me how to do the above steps?

Thanks in advance

Regards,

Devashish