is this correct?

[Zoe2008]

As per your verbally / verbal advised that the goods will be started mass production on 13 July in ABC factory. However, per Mr. Chan, the mass production date is planned to start on 20 July. Please double check and confirm for our arrangement.

 

[chester_100]

Hello Zoe2008,
I've made some big changes to the sentences. I hope it's of help.

Arrangements will be made as per/in compliance with/ in accordance with your recommendation to start the mass production on 13 July in ABC factory.
However, according to Mr. Chan's report, the mass production is planned to start on 20 July. Please double check and confirm for our arrangement.

 

[bertietheblue]

As per your verbally / verbal advised that the goods will be started mass production on 13 July in ABC factory. However, per Mr. Chan, the mass production date is planned to start on 20 July. Please double check and confirm for our arrangement.

The sense isn't completely clear and that's why my interpretation is somewhat different from Chester 100's. Anyway, this is my best shot:

"As you were verbally advised, mass production at the ABC factory was due to commence on 13 July. However, Mr Chan has requested that the commencement date be put back to 20 July. Please confirm acceptance of the revised date."