The idea of a truly "secure" server connection on the internet is certainly a topic of debate (as to whether it really exists) that could span a many page thread in "Off Topic". However, as to your question - call and order over the telephone, or FAX your order.
Many companies do not except full orders [order and payment] over the net as they don't feel comfortable with it either (SR Batteries gives a similar explanation as to their "online" ordering policy on their web site).
I personally feel that my credit card number and information could just as easily be stolen and used by that kid behind the checkout counter as it can if stolen off the web. That risk comes down to the protection your credit card company affords you, and has almost nothing to do with your trust in the company with which you are placing the order.
What secure protocal are you referring to? If it is Microsoft's 128 bit encryption, I suggest you personally research that encryption method, US ISC laws, and national IT regulations - to determine how much you trust it. If it is another, then the same logic would apply.
When you call, use a land line and not a wireless or celullar phone, that could be tapped and listened to as well by scanners...
Yes, personal privacy and protection from fraud is an issue that some believe is pointless, and others carry to extremes. Your information is out there - it just takes the industrious or lucky criminal to use it. The best you can do is never place three items of personal identification in the same location or same transaction. For the most part, your credit card number is useless without your mailing address. Your mailing address and ID is useless without your "numbers" (drivers license and social security). But you would be both terrified and surprised if you new what the various agencies (public and private) know about you and often sell to data centers (those companies that do "background searches" for $40 on the net, and tell someone everything you have done or thought about for the past 30 years.
Are there truly any secrets left? Only those your never told anyone and have never written or spoke about ever.
Just a little enlightened paranoia from the dark room... Cash