Interview Tips - Case Over the Phone

Hi all,

I just found out that I was selected for an interview for a summer position at M/B/B, the first round of which will be two case studies delivered over the phone (with the second round obviously being on-site). For those that have done this, are there any special considerations to keep in mind when doing case interviews over the phone? How do you still maintain a strong connection with the interviewer without eye contact, body language, and so on? How do they know you're not using a calculator in the background?

Thanks for your help!