Thanks everyone, really appreciate your help here.
Went to the dealer today and they admitted it was their mistake, agree to change oil and filter for free. However, I still couldn't believe such mistake was done by the dealer...
Car has been running with the wrong oil for 7 months now, only found out this week when I tried to file some old invoices on my desk, and noticed 10w60 was used for last service. Recent 3 months car runs like rubbish. Cleaned egr, intake manifold and replaced a new injector and forced regens, cost me a fortune. Car was still running rough, dealer got no idea how to fix, so just put some fuel additive in diesel, hope car can clean itself...this week engine light came on, it was a fault maf sensor.
Hope this time they can do the job properly, really disappointed with them.