Can't download App Store update for GarageBand.

I received a notification on my IPhone 6 Plus, IOS 8.4 regarding an update for GarageBand.

When I tried to down load it, it doesn’t down load. A message appears telling me to connect to Wi-Fi or else it wouldn’t down load.

IPhone is connected to my home Wi-Fi network and all works as it should. I get my email on my Gmail account, can watch movies etc.

I don’t use this app and no matter what I try I cannot down load it nor get that little “1” off the Garage Band icon telling me there is an update waiting to be down loaded from the APP Store.

I have no idea why it keeps telling me that I have to connect to Wi-Fi when my Wi-Fi is working fine.

How can I resolve this issue and either down load the update or get rid of it?

Thanks…