I've been thru **** with this freezing of contacts. I've had two SENIOR TECH's at Applecare, actually hang up on me and not call back - when they heard my problem with iPhone 5 contact app locking up the phone for up to 30 seconds. IMHO One issue is the algorithm they use which causes a search after one or two letters, then the phone hangs while the search goes on and I am unable to correct or further refine my query. There is now way I can type the rest of who I'm searching for in Contacts. The phone locks up totally for about 30 seconds, with letters that managed to get entered before the first or second keystroke, hang on the keyboard as if the phone is out of memory (3.9 GB overhead buy maybe not in system memory).
I have also force quit, restarted, switched off the icloud sharing which was causing a ton of duplication and quadruple duplication of contacts, further slowing down recovering from a wrong entered letter. Makes the contacts app totally useless. HELP APPLE. Where are the answers to our queries? Who can test my phone for memory usage or see whats obviously hogging system resources? HELP APPLE - four geniuses could not help, 6 senior advisers tried to help but didn't leave contact info or send as suggested and it seems impossible to get the same tech back. Further frustrating me as I have to retell my story to each and every person, including the two senior techs that actually hung up and didn't call back (not counting a fire alarm ending a call abruptly). Some Employee Bug is Eating You Apple!
Now with Applecare Senior tech on Mac side to rebuild the whole eco-system of MBpro, iPadMini and iPhone5, each with their own Apple ID and cloud account. The resolve hopefully will be restoring the iphone which seems the "backend" is suffering. I know there are the clogging debugging files that are created, which never leave the phone and after 2 years use, must be hogging some memory apart from the user file system. (shrug) good luck everyone!