I never had a problem toping up with my Austrian issued creditcard!
sims:
T-mobile AT (postpaid; former
max.mobil), [COLOR="Red"]telering (AT),
[COLOR="DarkGreen"]s-budget-mobile (AT),
Lycamobile (AT), ,
blau (DE),
giffgaff (UK),
no longer active sims:
orange (IL), At&T (US),
airtel (IN),
Tmo-US,
Hits (ES), Meteor (IE), VIP (RS), Telenor (BG)