To add subline under the service line which has been already billed in contract

Hi,

Is it possible to add new sub line under the service line which has been already billed. However service contract is active.

For example contract start and end date are 01-jan-2018, 31-dec-2018 and there is service line which has been billed on 01-feb-2018. Now is it possible to add new sub line under that service line and generate invoice for that.

We have below requirement..Service line has been already billed

We need the possibility to terminate a sub line in an active service contract and after termination to add a new sub line. If the total amount of the contract is higher than it was, we need to have the possibility to have an invoice.