Skyetel uses the From header to acquire the CID. The CID filed in the extension settings should be left blank. When set to be blank, the extension number is used by default.
I am curious as to where the “+” sign is being inserted in the From and To headers. Look in the PBX Settings, General and if something is there, remove it, I also note that the “1” is also in the field; yet the CID you had shown for the extension had neither the + or 1, which makes me think some other field in the UCM is populated with same.
The DR 4 is in quotes and should not be an issue as the is the SIP Display Info. The +15303420518 is the data of interest as this is the SIP User Part and the following IP address is the Host Part.