Modifying Invoices

[Nestor Stura]

Hi all,
I need to modify several old invoices, mainly deleting the job field
that complicates my reports.
I have tried doing:
1. Unposting the invoice.
2. Editing it (deleting job field)
3. Posting the invoice back (changing dates to original)
4. Re-paying the invoice. (with original date)

At the end I could do it, the invoice appears posted, paid and without
job. The problem is that after that process I find several
transactions in Accounts Receivables (negatives and positives) that I
do not remember generating them (lol) and that requires another
deleting and cheking, otherwise the customer report is a disaster.

Is there a formal or logical way to do this operation? Whithout this mess...

Thanks in advance,
Néstor