If you would have searched you would have found this thread http://forum.tipb.com/verizon-iphone...4-2-7-a-2.html which has this info
Steps to downgrade from 4.2.7 to 4.2.6.
Step 1: Make sure you have your SHSH blobs saved. A way to check this is to download TinyUmbrella, connect your iPhone to your computer, and then once it recognizes your phone, click Save SHSH blobs. It will then verify if you have them saved in the log description.
Step 2: Download the 4.2.6 ipsw file. There are links all over if you just search Google.
Step 3: Open iTunes and put your phone in DFU mode. Then, hold down the shift key and press restore (hold down alt key for Mac users). Then find where you have your firmware saved and select 4.2.6. iTunes will then ask you to press restore.
Step 4: iTunes will restore 4.2.6 on your phone, and here is where you might get the 1013 error, which makes your phone stuck in recovery mode.
Step 5: Download Greenpoison rc6.1. Put your phone back in DFU mode and then run Greenpoison to jailbreak your phone.
After greenpoison does its thing, your phone should boot back up with 4.2.6 installed and you will be jailbroken.
I'm not trying to be harsh OP but when I see the same questions asked that have been asked time and time again it's not fair for someone helping you to do the hard work. If you are having the problem you should want to do the work yourself.
Grunt I wish I would have talked to you before you took the phone in because once you were back to whatever firmware you went back to, with the error you could have just put the phone into DFU and run the tool but anyway we live we learn LOL