In reply to Jose Carlos.

Hi Jose,
Unfortunately there is no fixed software for the 9971s yet. When we have it we will update the info in the Fixed Software section of the Advisory http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20140409-heartbleed#software

Note that if the phones are deployed using the proper best practices (voice VLAN, not accessible inbound from the internet) then someone on the internet would not be able to exploit this. Also, the HTTPS server is currently not enabled by default on the phones. So, I would check if you can access them over HTTPS because there is a good chance you are safe already.
I hope it helps,
Panos