Many ppl had some subbing issues last time, me included. Today i renewed my premium account w/o any problem. Thats what i did:
First of all use only this account page https://register.ageofconan.com/account/
Cancel your running sub and let it run out. Make sure you are downgraded to a F2P account. Click on upgrade to premium account and follow the steps. Worked fine for me and took me 10 min.
PS: You have to unlock all your chars again, make sure your account has turned to premium before you do it or you will lose your AA time training progress. Happened to me on the char i play now and have to train it from start again and it was so close
Anyway i hope this helps a few ppl