call them with their fathers names – this is more suitable in the sight of allah and if you do not know their fathers then they are your brothers in the faith and your friends and there is no sin upon you for what you did unknowingly in the past – however it is a sin what you do with your hearts intention and allah is oft forgiving most merciful.
ادعوهم لآبائهم هو أقسط عند الله فإن لم تعلموا آباءهم فإخوانكم في الدين ومواليكم وليس عليكم جناح فيما أخطأتم به ولكن ما تعمدت قلوبكم وكان الله غفورا رحيما