Adding To Orders Issue

[TheSouthCloud]

Good Morning All,

 

We need some assistance with adding new orders to customers. We have a whole load of customers currently set up on WHMCS paying monthly amounts through Direct Debit system which works great. The system raises the invoices automatically on a particular date every month as per the configuration per product.

 

Some customers are now purchasing more services for example email accounts, which are billed on a monthly basis.

 

How can we add these new orders to a customers account, but then it add these services to the customers next invoice and then continue raising invoices for the new amount of old + new additional service on a monthly basis?

 

Tried this will billable items - didn't work so well but as I understand it, this is not the correct use of Billable Items anyway?

 

Any help greatly appreciated.

 

Thanks,

Toby