QB Issue Resolution:

if you are within the first 60 days of starting the account, see this

otherwise it is easier to cancel and create a new account, cause you would have to bring up each transaction and delete each one, one at a time

Resolution for Issue 'How do I start over with a different company file?' available: Yes (Solved).
Source: Intuit Community forum.

How do I start over with a different company file?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Company File
Quickbooks Repair Pro will resolve it efficiently and affordably. Guaranteed resolution of your issue, or you pay nothing!

Error Recovery for Company File [Canada]
E-Tech is the #1 Quickbooks data migration and Conversion service provider.

Get 50% off Quickbooks Online

Click Here for 50% off!

Additional Support Options: