Verda Tech

I got Verda Tech to check my house for an energuide report last year. They said my attic had an R value of R30, but I'm not sure about that. The guy only looked for a few seconds and my house is over 60 years old with old insulation. I got 3 other companies to check and they said it's R12, R15, and R16. Verda Tech's report goes to the government for a rebate, but if they're wrong about my R value, I won't get as much money back. I tried calling and emailing them, but they won't fix it. If they checked again or changed the report, it would be better. It's hard to believe 3 other companies are all wrong. I have 3 quotes that show the old insulation value too.