In the customer module there is a display name which we want it in default as company name, please guide for the same

I'd be happy to guide you in changing the default display name of your company, @bhaveshwarcompu.

You can copy that display name in the Customer module, then enter that in your QuickBooks account profile to update the company name. Here's how:

1. Go to the Settings menu, then select Accounts and Settings. 
2. Navigate to the Company Name, click the pencil icon to edit the sections. 
3. Update the Company name field.
4. Make all other necessary changes on that page. 
5. Click Save, then Done. 

You can also check out this article for further insights: Edit company settings in QuickBooks Online. 

For future reference, you also want to add another company instead of just changing your business info to keep your books separated for tax purposes. 

Let me know if you need more help in updating your business name. I'll be here to be your Quickbooks guide.