Does your baby rejects Frozen breastmilk? If yes, how did you solve the problem?

It could be due to the difference in taste. Sometimes the taste of the milk would change due to the storing process. For example, there may be excess lipase in the milk due to the storing and causes the frozen milk to taste soapy after being thawed. The way to go about this is to scald the express milk first before freezing (you can refer to this blog post on how to scald the milk: http://simplyrebekah.com/2010/05/03/excess-lipase-scalding-breast-milk/).

At first my son also reject, I mixed with fresh milk.. I did tried also mixing with formula as I don't want to waste my fresh milk if he can't finish (30ml formula 90ml frozen), but in the end he accepted it after 1mth... I giv him one pack of frozen a day the rest is fresh milk...

Try mixing part FBM with chilled EBM first, starting with more EBM, then slowly reducing the amount of EBM until fully FBM. It worked for my LO. Sometimes they just need a bit more patience in introducing instead of going straight to full FBM at first instance.