Tax Exemption

Hello,

We are a tax exempt organization, but we continue to be charged sales tax each month. I have reached out to Comcast on this issue on at least 4 separate occasions since January by phone and email, and I have provided our sales tax exemption certificate three times. I have been told that the tax exemption certificate has been forwarded to Comcast's tax exemption department. What else can I possibly do to get this issue resolved?

Thanks.