Update/Change GSTIN in GST Settings of zohobooks

Update/Change GSTIN in GST Settings of zohobooks

We are trying to update our GSTIN under the GST settings section of our Zohobooks account 
Initially, we had entered a dummy GSTIN (123456789123456) to generate a sample invoice before obtaining our official GST registration.
After receiving our actual GSTIN , we unfortunately forgot to update it in Zoho at the time. We are now trying to make the correction, but are receiving the following error message:

"Cannot change the GSTIN since taxes are associated with transaction(s). Delete the transaction(s) to proceed."

We kindly request your assistance in updating our GSTIN without having to delete the existing transactions, if possible. For almost one year there was no problem in creating the invoice, but now while creating invoice, IGST is being applicable as tax instead of cgst/sgst. Deleting all the transactions is not practical as we are having huge data. 
The customer care informed the only way is to create a new organization and migrate all the data.
So we have started doing that.
But I feel there should be an alternate option to tackle this problem.