The present invention relates to charging of communications using chargeable resources of a first communication system and a second communication system wherein at least one of said communication systems provides wireless communication services. In accordance with the method, after a set-up procedure for communications initiated a first procedure for obtaining a first charging component is triggered, the first charging component being associated with the first communication system and determined based on a first charging model. If required, a second procedure for obtaining a second charging component is also triggered, the second charging component being associated with the second communication system and determined based on a second charging model. Information associated with the communications in the first and second communication systems is processed simultaneously to obtain the respective first and second charging components. The first and second charging components are combined to obtain a total charge. A prepaid balance is then decreased during the communications based on the total charge.