Hello Maria,
This message can be suppressed by the functional settings in OVA8.
Goto T.code OVA8 --> select the entry applicable for you ---> click on display icon.
A new screen would appear like below.
You can either uncheck the Dynamic credit checkbox or change the reaction to <blank> or anything in F4 help.
You can also create a routine and assign it under document controlling --> No credit check.
Do a F4 help in that routine field and refer to the standard routine "001" available in system to get some idea on how to use routines.
Regards,
Thanga