Maffen, let us help you out with your grammar!
You should start the sentance with 'The' and not just 'customer'........plus use a capital at the start of a sentance!.........So......
The customer is king...........(note no capital used for king).
Next mistake is the missing space after the commer, such basic errors.......tut tut.........again.
The customer is king, but not with you..........and another grammatical error, you should have used another commer after 'you', thus.
The customer is king, but not with you, ........oh dear another mistake Maffen, the use of the lower case i is incorrect, you should have used a capital 'i' like this 'I', now let's see how it works now.
The customer is king, but not with you, I reckon...........oh dear you missed out the full stop at the end to finish the sentance. Shall we do it for you?
The customer is king, but not with you, I reckon.
There you go Maffen, not very difficult is it?
Now when you have mastered the art of the English language, I suggest you crawl back under the rock you came from and not bother us again with your drivel.