Here is a quick plan of action of what to do next if the phone interviewer never called -- finding out what went wrong and how to resolve it quickly. My first suggestion to you, as obvious as it sounds, would be to 'double' and 'triple' check again, the time scheduled for the phone interview to actually happen. Whether that message was in an e-mail they sent you or message on an application account -- make sure you have got the right date (check both the day and month) and the right time, and re-read any additional instructions they may have sent you. You will be surprised at how many phone interviews were missed simply as a result of failing to get the right time or finding out that it is in fact in another weeks time.
If you have got the right time, my second suggestion then would be to immediately go over to your application form for the internship phone interview or job interview you submitted -- as perhaps when it came to writing down your telephone or mobile number you may have typed in the incorrect number - perhaps your old number by accident, or have missed it by a digit. Hence, why they couldn't get hold of you, as the incorrect number was provided. Another possible reason may be due to bad signal and connection on your end hence they struggled to get in contact with you. If you have the correct number and the right time then follow the procedure below.
You now need to get in contact with them. I would firstly send an email (to any email address you deem relevant, from the department you are applying to, to a contact us help email, the more you send it to the faster you will get a response and clarification as to what has happened -- also a better chance it gets to the right people) detailing the situation you are in, whether you have made a mistake (you gave the wrong phone number, got the wrong date and time), or you don't know why and that you simply didn't get a phone call, and ask what can be done from that situation onwards -- politely.
I would then go on to ring the relevant department or help line ('contact us' number) explaining that you have sent an email as well as the situation you are in -- you received no call, and that you hope to be scheduling the phone interview again -- promptly. Then hopefully they should be able to get back to you soon and sort out the new situation as to what went wrong (if you didn't find out) with a new rearranged time for the phone interview to take place -- you may find it to be later that very day (or even the very next day). You are probably likely to find out they either had the wrong number for you (through their own mistake or yours), or they may have simply just forgot. Let me know what happened to resolve your situation and if you have had any experience of a phone interview that never called -- please share your experience below as well as any tips to help resolve the matter.