I can assist you in identifying the reason behind the client's name appearing after every estimate number and guide you through the steps to resolve this issue.
It could be that the Custom transaction numbers feature is enabled. Or someone modified the estimate and entered your client's name.
To verify if it's enabled, you can go to the Settings. Here are the steps:
Click the Settings icon and select Account and settings.
Choose the Sales tab.
In the Sales form content section, toggle off the Custom transaction numbers.
Click on Save, then Done.
Additionally, you can utilize the Audit log to verify if someone made changes to your estimate and include your client's name. Go back to the Settings icon, then select Audit log.
Moreover, I've got these articles to help personalize your sales forms inside the program: