minecraft realms cancel subscripton help

I signed up for minecraft realms through mojang/iTunes on my son's ipad. According to our mojang account, the 1-time (1-month) subscription expired some time ago, but I have since then received 2 monthly charges from iTunes for the continued subscription. I cannot figure out how to cancel it through iTunes, and as I said, we don't actually have access through mojang/minecraft. Does anyone know how to sort this out? I am on an hp.

Thanks!