Cannot link my credit card

Hi<br> <br> I cannot link my credit card to my online account. I phoned the call center and they told me it was not possible to do online!!?They sad I have to go through dialing numbers on my phone and I refuse to put credit card details into my phone due to the risk involved .Is this true? I am already paying a lot for my contracts and now I cannot top them up with my card.<br> Its like you don't want money. Give me a way to purchase data with my credit card ONLINE or I am moving providers.