someone locked my daughters iphone

Hello!

my daughter phone was recently locked and bound to someone else apple ID and i cant do anything to it. basically i cant find any reasonable way to get a support from Apple browsing apple.com website

it was all time bound to my apple id now it says it s bound to r*****@icloud.com

in fact apple easily may trace its usage it was used ion Slovakia and all time belong to my ID mentioned above (and then restored from iPod5 used by my daughter) . i cant say whats happened - may be someone on school entered hackers data. done know. just a 2 days before new year after reboot phone (full power cycle) started asking 4 digits pass

please help me recover it and remove lock ! this is our iPhone 5S and always has been

just let me know what to do and who to contact and mainly how!!! i will provide IMEI, etc my ID upon request.