Paying your loans can be stressful for many reasons, but a top source of anguish is dealing with the people at the other end of those loans—typically, a faceless bureaucracy that likes to send form letters and put you on hold over the simplest of questions. Sameh Elamawy, the founder of a San Francisco startup called Scratch, thinks he can help. Elamawy has assembled a team of Amazon and Pinterest veterans to recast the loan servicing business as a friendly, easy-to-use app.