Push notification advertising for call campaign, anyone have any success so far?

I am using push notification to promote call campaign at the moment and seeing some positive ROIs. Was wondering if anyone here is using push to promote call campaign offers? Using Megapu.sh currently and was wondering if there is any other push notification network that allow direct linking to the phone number. Direct linking to phone number instead of landing page seems to result in better conversion rate in my case. So I am looking at ad network that allow such direct linking to phone number. Any advice will be much appreciated.