I have booked Eurorail global Pass, for travel around 4 countries including Italy. But I could not do my reservations on the trains online, I expect to take around these four countries. Can the payment for the reservations be made at stations in Italy through International Credit Cards?
Can I make all the reservations at one station, say Roma Termini?
I don't know why you couldn't make reservation online, it should be possible. What went wrong?
But (1) some trains (Regionalle in Italy, nearly all trains in Switzerland, regional in other countries) do not have reservations. It is not possible.
(2) French TGV trains have a limited quota for Eurorail holders. If this is used up, hard luck, buy a normal ticket.
I would only expect an Italian Railways station to be able to book tickets for Italian trains, and International ones to and from Italy. Not for other countries or other railway companies.
You will need some cash in Italy (Euros). Credit cards will not suffice for everything.
P.S. Did you tell your credit card company you were making "foreign" purchases? Perhaps they blocked the payment as "suspicious".
For others (not the OP) who see this thread, you should know that rail passes rarely make sense for travel within Italy. That's not to say they don't make sense for the OP, but don't assume that if you're traveling in Europe, you need a Eurail global pass. Do the numbers, and then decide.