How can people with debilitating social phobias get through foreign language?

First, social phobia is not a character defect. It is a recognized medical condition. You are not worth less as a human being if you suffer from a phobia.

Next, depending on your school, you may be able to get a medical exemption from certain requirements. You may want to discuss this with your local student services. (By email if meeting people in person is impossible to you.)

However, I would strongly advise against this approach. You will need to interact with people after leaving college, too, so avoiding the problem is not a good strategy in the long run. Instead, I would recommend that you actively work on this issue.

The good news is that social phobia is very amenable to cognitive behavioral therapy (CBT). The accepted form of therapy is a desensitization approach, where you will progressively learn to tolerate being around people.

No, this will not be easy. You will need to work on your disability. You will encounter setbacks. But your student services should again be able to point you towards resources and therapists that can help you. And there is no better time for doing this therapy than now, when you have a more-or-less flexible schedule, and before you hit the job market, where social phobia will be an enormous problem - regardless of which career you want to pursue.

Good luck!

I am not aware of your location, but I can comment on the position in the UK. If a student (or academic or researcher) declares a disability to their institution then (together with clinicians or other appropriate evidence and an assessment of need) they are required by law (Disability Discrimination in Education) to make provision and adjustments (except for where the adjustment would be unreasonable). Only the courts can rule what is reasonable or not.

However, an individual may choose to keep their condition private, in which case the institution has no obligations until the point of disclosure. Privacy law overrides disability law in such cases.

I have responsibilities for students with alternate needs in my subject area, and this includes students with social phobia conditions. Some as extreme as you describe.

We have, for example, conducted oral examinations and tutorial using skype between two adjacent rooms so that the student does not have to share a space or be overlooked by another person.

It can be done, if there is a will and a motivation to do it on behalf of the institution.

Edit: however I also strongly concur with Stephan's answer. When a student has declared they are offered help and support. In particular CBT and other therapies are very helpful in putting students and staff in better positions for employment and promotion.

... I paced about in front of the building trying unsuccessfully to force myself to enter the classroom. ...

I'll be honest with you. If you cannot get over yourself and force yourself to face your fears, there's little point in getting your degree, since you're extremely unlikely to land a job that requires a degree in which you could function.

If you don't want to quit, my advice is to deliberately seek out social occasions as often as possible. Face your fears and try to desensitise yourself to your phobia. It will be hard, but it's the only way.