Yes no problem. Depending on where in the order process is you might have to wait until activation for the speed change to happen, which generally is within 24 hours from that request. This is because there isn't a way to amend an existing order nor is there an ability with their backend to submit two orders on the same account so basically we have to wait for the install to complete and then submit the speed change.
I suspect the phones may be a little busier than normal tomorrow, if you get a queue you can always just send an email to email@example.com with your account # and your instructions and they'll be happy to help you out that way too.
Oh, and welcome aboard!