There are times when a phone call is actually the easiest way to deal with it. I have been able to link old accounts without calling, but I also did need to call once (got some poor dude as he was getting his morning coffee, eh eh.)
One key to remember is that when you first set things up, you must place _uo after your original account name. So if the account name was pwnseveryone you would need to type in pwnseveryone_uo into the account management system in order to get started with it.
The next thing to note is that after the account pops up, you will be at a screen where it lists that account name as pwnseveryone - Ultima Online. In the upper right hand corner of that box there is a button labeled "set description" - you must hit this button once. But you only need to do that the first time, when you are setting the accounts up.
If you have multiple old accounts, you'll need to do that for each one - but then, after they are all set up, you will be able to choose which account you want to work with from a drop down box at the top of the account management page. If you add any new accounts, they will be shown on one of those pre-existing accounts rather than showing up in the drop down box.
Finally, I have found that it's easier just to purchase 6 month game time from the UO store and input the code than to use the 'bill my credit card monthly' or every 6 months or whatever. I used to use the credit card billing system, but the game codes negate any issues with billing card numbers, addresses, etc. When they first implimented the new billing system, I literally talked a number of guildmates through the process. It should still work the same. But if you do have issues, call them. I might be able to locate the 'best' phone number if I dig through posts on my guild's website.
I don't know if any of this helps, but hopefully it will. Oh - I think I might have even posted a step by step here on Stratics when they first started the 'migration' thing. So you might search our Siege forum here for 'account management' posts by me.
