After you file

I have a payment plan in place.  The mortgage company insists on a letter with the installment agreement.  I've spent about 5.5 hours on the phone with the IRS trying to make this happen and I just can't seem to.  Three different people I've spoken with have told me they could do it, set it up to fax and the faxes never come in.  I've tried a different fax line each time.  Every other time I call, no one will help me.  They tell me that it's not possible to get this letter.  Not really sure what to do now.