After the service contract is signed, the Change Status field value is automatically set to Locked. If you want to modify information in the service contract or service contract quote, first you have to change the status of the contract or contract quote from Locked to Open. Note that it is not possible to create sales invoices for the service contract with the Open change status. After the contract or contract quote is modified, you have to change the status back to Locked to make it possible again to create sales invoices and ledger entries for the service contract, including the changes that you made to it.