Always check if your API call was successful or resulted in error. You may check the following

200 OK response header.
4XX ERROR response header

Please check the table below for common error constants. Note that some API functions can return custom errors of their own (listed in appropriate document sections). Check the error description for details, e.g. which field caused an error or which resource you don’t have access to.

CODE	HEADER	DESCRIPTION
SUCCESS	200	OK
AUTH_FAILED_NO_DATA	401	You have not provided auth data.
AUTH_FAILED	401	The auth data you have provided is invalid.
NOT_IMPLEMENTED	404	The method you are requesting is unsupported.
OVER_LIMIT	429	You have exceeded the request limit.
FIELD_EMPTY	400	Required field is empty.
FIELD_INVALID	400	Field has invalid format (see proper format in the description).
NO_ACCESS	400	You don't have access to this feature
KEY_EXISTS	400	The resource with this key already exists.
LEDGER_ERROR	400	Insufficient funds to carry out debit
BAD_CALLER_ID	400	The sender ID you have set is not valid or number is inactive or expired