Salesorder error messsages

[JUKKA BLOMQVIST]

Is there a place where SalesOrder API error messages are explained? I have two error messages, which I do not know how to solve. Messages are 

"Invalid Customer Contact, or Customer Contact not found" and 

"Currency Id can not be overridden"

[Yıldırım]

Hi, the best way to diagnose such cases when you're unsure about what Field / Value causing the error, is trying the same operation in the Financials ERP UI with the same values provided in the API, hence the system can highlight you the errors and shows how this can be resolved. 

[JUKKA BLOMQVIST]

Thats the problem, I can open salesorder for the same customer I have in API with different currency, and get list of contacts there too. I get rid of the currency error if I remove currency-item from API-message (Customer update shows that currency change is allowed..), with the contacts I can't find the id (integer in schema), just the name.