Calendar events picking the wrong organiser.

When I create a calendar event and send it to invitees it doesn't select my contact details as the organiser and uses another contact's details. The recipients see this other contact as the organiser and the reply email address belongs to the other contact. This is not random in that it selects the same wrong contact details each time. Is this something that is corrupted or can it be reset? I have made changes to the other contact details to prove the error, such as changing the email address to mine and it uses my email address as the reply address. However, it does not recognise the change if I change the contact name which implies it is either corrupted or it gets part of the information from another source. Any ideas please?