Suddenly, when my annuity was due, I no longer existed!!!

I have an annuity which should be paid into my account annually on 14th Nov. This year no payment arrived. I contacted them and was told that because they had written to me and I had not replied they had cancelled payment as they assumed I no longer existed (I never received the letter as I live in Spain and the postal service is abysmal). I forwarded documents to them by registered post to prove I was still alive and proof of my address. They received these on 10th December. Following numerous telephone calls to them to find out when my annuity would be paid I finally was told on 18th Dec that payment would be made by electronic transfer that day. Nothing arrived. It is now 29th Dec and so far today I have telephoned them 4 times to find out when I will receive my money. Each time they promised to call back but never did. Every time I call them I get a different story and different excuse, and have to deal with a different person. My pension is now 6 weeks late and this has caused considerable stress and hardship. It has ruined our Christmas and I still dont know when or if I will get paid. This company is using delaying tactics at every opportunity to avoid paying on time.