cellc just wants sales

I took a contract for my dad on the 24/11/2017 an iphone 5s that was going on special for R129. The manager from cellc la lucia named astaan came to my house and delivered the iphone to me. he also told us he will set up the iphone for us. over 5 months now my iphone has locked my dad is unable to unlock it as we do not know what the manager had setted his username and password I have made numerous attempts to recover this password I am unable to. my phone is still brand new condition but I am paying for a phone that I cannot even use. he did not even write down my passwords and usernames that he set up.Please can someone help me