How can i unlock my iphone from a Japanese carrier???

I have bought an iphone 5s from Japan and it worked fine until i went to my service provider to check why my 3G wasnt working. My service provider then told me that my sim card wasnt being read by the phone anymore after she reset my network settings. My phone is apparently locked to NTT Docomo and Vodafone told me to email them, but all i get when i email them is an automated msg giving me a referance number which is practically useless because they never followed through and its been 2 weeks now. Even this morning i emailed them with the referance number they gave me and all i get is the same email they had sent me in the very beginning saying..

Thank you for your interest in NTT DOCOMO.

We will do our best to respond to all reasonable inquiries in a timely manner.

However, please note that some inquiries may take longer to address depending on their nature.

Please also note that auto reply does not guarantee that your inquiry will be addressed.

and then underneath my referance number again.

I have already spent a lot on this phone and all these sites offering to unlock my phone for a price which is not guranteed makes me wonder if its safe or not.

The wierd thing is that i had bought 2 others mobiles for my dad and cousin when i bought mine and they are both working fine!