Sorry to hear you've had problems with your overseas subscription. I'm not sure you'll have much luck with the normal TF subs telephone number because you paid for your subscription via imsnews.com. But by all means, you should give it a try.
What about stopping the imsnews direct debits, seeking a refund for the issues never received and starting a new overseas subscription directly with TF/Future Publishing: http://www.myfavouritemagazines.co.uk/
Let us know how you get on.