Can't purchase online for the last week.

I have been trying to purchase items online for the last week, most of which were on great specials at the time. I continue to get 3D secure blocks on my account. I have phoned the call centre 4 times in the last week and they have been quite friendly and helpful. But even after clearing the blocks and updating my details over and over I still cannot use my card online. I have lived banking with you, but perhaps it is time for me to move to a better bank, that would actually be willing for me to use my card online, or at least assist me better with these types of issues