ISSUE WITH VALIDATION FIELD

I have a problem with a validation of field of a service request. My problem is this:

I created this type of validation for the field STATE:

([<Status>] = LookupValue ("SR_STATUS", "Open") AND
[<AccountName>] = 'TO CHANGE') OR
([<Status>] = LookupValue ("SR_STATUS", "Open") AND
[<AccountName>] = 'TO BE DEFINED') OR
([<AccountName>] = 'SPAM') OR ([<AccountName>] 'SPAM' AND
[<AccountName>] 'TO CHANGE' AND [<AccountName>] 'TO BE DEFINED' AND
[<plReason_of_the_contact_ITAG>] LookupValue ("OCC_CUST_LOV_
SR_10 "," To be defined "))

Now say that the field "Account Name" is set with 'TO CHANGE' and the field "Reason of the contact" is set with "To be defined" and I try to close the service request, the validation works correctly and blocks me to closed the SR ([<Status>] = LookupValue ("SR_STATUS", "Open") AND