Hi amina02014, I think ios 8 and 9 are not compatible with an iPhone 4. You have to open a safari browser and go on the page below to put the APN setting : http://www.unlockit.co.nz/ Take option: Canada, Public Mobile and Create APN.
In first, welcome to public mobile. Your number can be take 24-48 hours to be transferred. You have to wait couples hours more for your inbound call works with public mobile.
Vous pouvez poster vos questions en anglais dans le lien ci-dessous : http://productioncommunity.publicmobile.ca/t5/Public-Mobile-Community/ct-p/Public_Mobile_Community
