What data recovery store did you take it to? How did they come to the conclusion the NAND is damaged? The only way to retrieve the data is to get the phone to boot; this is why you need a reputable repairer that if necessary can perform CPU transfers if the board has been damaged. I would contact stores like Ipad Rehab, STS Telecom and RESQ and explain who you took it to and what repair they tried. I find it unlikely the NAND was damaged before they tried the repair.