I've got a Wiko Iggy on 4.2.2 Android and try unsuccessfully to bind both numbers of a workmate on one sms chat.. what should I do?
Contacts+ will do that for you.
It will also let you have one fixed primary "to send" number.
It's great if you only want to send to one of his numbers and he only wants to send from the other. Your workmate texts you from number X and you just have to write and send and the sms will be sent to number Y automatically.