Issue about Asterisk Active Calls increasing

We have an issue about Asterisk Active Calls.
We use Asterisk-
Sometime, the active call increase to a big number quickly (several thousand) and although the channel is very small ( about a few dozen) after run Asterisk server some aleat of minutes.
We think that some calls that got hanged up by caller but asterisk channel didn’t get free for these calls.
Have got any one ever get it yet ?
Have got any one ever fix it yet ?
If it was fixed, please show me what is version.