Try to use "Sixg Txo" Chinese Newspaper Classified! Lots of ad and most of them charge extremely low $ and not charging per hour!! lots of them even say won't charge any if not successed! I tried to call years ago from that ad. and luckly it works!! (also kitchen sink) GOOD LUCK
how come your kitchen sink was so 塞. You wash everything like coffee grounds, tea bags into it? Normally if it can pass the P-trap it should pass out to sewage without problem.