Citibank released a pair of videos yesterday designed to teach customers how to use online bill pay and mobile check deposit. The videos are comprehensive — each other more than two minutes long — and are not marketing material as much as tutorials. The level of detail is admirable. For example, viewers are instructed not to answer calls or reply to text messages during the check-deposit process. Users are also warned about deposit limits when they begin the process — a nice touch, and an unusual one.