How much do you trust a tax firm to appeal your property tax?

[Becky Lu]

We used a company to appeal for our small apartment in Houston (Harris County) this year. The result just came out. The initial assessed value was $890k and the final $820k. According to the bill they sent us, they've lowered almost $70k in value, which translates to about $2k saving on our property tax. The company is charging us  25% of it. I questioned them on their initial assessed value cause our appraisal was no where close to $890k and we bought this property only 4 months ago. So I'm curious if the company just made up some number and tricked us to believe they lowered the value and charged us for the work they didn't do. Any thoughts? I hope I'm not being too crazy.... 

Thank you!