As you folk between you all have solved the rest of lifes problems this has to be an easy one.

Possibly a UK/ European thing but needs to work in the USA

I have a main Mastercard with a high limit that I do not use online.

I used to use Freeserve as my Email handler and signed up to there online credit card, Freeserve marbles card, I use it for online purchases and when I travel and think my card may be stolen. I keep a reasonably low limit £1500. Since the day I had this card I have had 10 times the problems of my usual Mastercard especially when my wife talks to them, we have now sent 3 recorded letters giving her authority to speak on my behalf and she also has a card on the same account in her name.
Still its not good enough... so enough is enough.

All I need is a card that I can access online and is useable all over and does not ***k me about all the time. ( I wont bother to list all the ***p that I get all the time off them).

Knowing nothing about credit cards I had presumed Marbles Mastercard was big, Is Freeserve Marbles just a small agent for Mastercard.

I am baffeled please offer a good option.
Many thanks in advance.