SIP Calls not clearing properly

Asterisk Asterisk Support
1

I have noticed that I have sip calls that don’t seem to be clearing properly.

iti-ibex01*CLI> show channels
Channel              Location             State   Application(Data)             
SIP/199.37.112.100-6 (None)               Up      Bridged Call(Zap/155-1)       
Zap/155-1            01179036883793@att_s Up      Dial(SIP/79036883793@199.37.11
SIP/199.37.112.100-e (None)               Up      Bridged Call(Zap/152-1)       
Zap/152-1            0112348033233329@att Up      Dial(SIP/2348033233329@199.37.
SIP/199.37.112.100-0 (None)               Up      Bridged Call(Zap/150-1)       
Zap/150-1            011582812622491@att_ Up      Dial(SIP/582812622491@199.37.1
SIP/199.37.112.100-1 (None)               Up      Bridged Call(Zap/145-1)       
Zap/145-1            01148343506321@att_s Up      Dial(SIP/48343506321@199.37.11
SIP/199.37.112.100-9 (None)               Up      Bridged Call(Zap/161-1)       
Zap/161-1            01178137158618@att_s Up      Dial(SIP/78137158618@199.37.11
SIP/199.37.112.100-9 (None)               Up      Bridged Call(Zap/166-1)       
Zap/166-1            011639205218570@att_ Up      Dial(SIP/639205218570@199.37.1
12 active channels
6 active calls

iti-ibex01*CLI> sip show channels
Peer             User/ANR    Call ID      Seq (Tx/Rx)  Form  Hold     Last Message   
192.168.1.109    (None)      3c105b5-ed0  00101/45999  unkn  No       Rx: REGISTER   
199.37.112.100   7903688379  5de12625725  00102/00000  g729  No       Tx: ACK        
199.37.112.100   2348033233  5d4f02077ef  00102/00000  g729  No       Tx: ACK        
199.37.112.100   5828126224  2e082a6c731  00102/00000  g729  No       Tx: ACK        
199.37.112.100   4834350632  12c0f958761  00102/00000  g729  No       Tx: ACK        
199.37.112.100   7813715861  1a57edf758a  00102/00000  g729  No       Tx: ACK        
199.37.112.100   6392052185  23cfb451494  00102/00000  g729  No       Tx: ACK        
199.37.112.100   6113006592  26c5ae7f79d  00103/00104  unkn  No  (d)  Rx: BYE        
199.37.112.100   6113006592  397c5573634  00103/00104  unkn  No  (d)  Rx: BYE        
199.37.112.100   1206345002  0b24bf307db  00103/00104  unkn  No  (d)  Rx: BYE        
199.37.112.100   6113006592  5759ddb664b  00103/00104  unkn  No  (d)  Rx: BYE        
11 active SIP channels

Notice the “Form” column, the items that indicate “unkn” are the calls that don’t seem to want to clear. I get a new item about every 12 to 24 hours that adds to this list.

Any thoughts on this, I assume this is not good but don’t quite understand how I can clear these calls out of the system.