Aer Lingus - Refund ?

I booked a return flight for 4 people. In December I got an email to say the going out flight time had changed to much later in the evening. I got an option to accept this or get a refund. My father is travelling with me and the flight time is too late so we decided to cancel the ougoing flight and keep the return flight. I spoke to an Aer Lingus agent on Christmas Eve and he went through my options. I told him I would cancel the outgoing flight and he said I would get a full refund. By the second week in January I still hadn't received the refund. I rang and was told the refund was being processed and would take 28 working days. Today, still no refund. I rang this evening to be told there will be no refund until after I take the return flight ..... which is in September !!! And even then I have to apply for it again. I can't believe or understand this. Any advice on how I can get my refund sooner?