Change country in Apple ID

Having recently relocated to Switzerland from Greece, I can not change my credit card details under the Payment section. Have even cancelled the iCloud storage upgrade I had, because I read that payments could be a reason for "blocking" me from being able to alter the payment details. The storage upgrade has now been cancelled a couple of days, have no other payments (iTunes etc.) but still can not change credit card and country details. Any idea on what I must check please ? Many thanks all...