In order to track call data from an eDM you need to add additional code to the referral URL link placed in the eDM.
The additional code is ?utm_plasource=edm
Therefore for example if the URL is www.mylandingpage.com/business/abn.html
Then the URL will be www.mylandingpage.com/business/abn.html?utm_plasource=edm
Additionally, if you also want to name the banner, then you need to add additional information, such as
www.mylandingpage.com/business/abn.html?utm_plasource=edmname