Circular dependency

i have 2 tables, customers and salesteam. in the customers table, i have a column sales team that was added with a lookup() dax function that gets the Salesteam[salesteam.name] by doing a lookup on the salesteam[salespersoncode] that matches the customers[salespersoncode]. i dont know why it was done like that,  but there was a dependency error in the relationship when we tried to remove that salesteam column and just do a relationship between both tables on salespersoncode.

i want to make a relation between both tables, because my row level security that is filtering on the salesteam wont work where the salesteam filter is taken from the customers table. when i tried to make a relationship for both tables on [salesteam], i got an error :
circular dependancy was detected : customers[salesteam].

any suggestions to fix the issue?