I believe the only value of Bible Call is to use it in conjunction with a correspondence course. You change the tape daily and mail the first lesson to those who request it. A good quality answering machine is usually the most economical investment. Avoid endless loop machines. A variable outgoing message machine is a real time saver.
Newspapers are a good way to get enrollments.
The ad should resemble a coupon which advertises the course and provides a space to fill in their name, address, and phone number. The newspaper coupon is then mailed to you. Also try the classified section, i.e., instruction courses, wanted column, and personal column. Advertise for Bible students in the wanted column. Print handbills and place them on the windshields of cars.