Deducted money without me applying or approving

Last year i unsubscribed and was never bothered by the company again. I did and still do not have the finances to pay for the service and thus the reason I did not keep the subscription. No problem they were friendly and assistes no hassles..... This month out of the blue i see they deducted monthly subscription that i cannot reverse from my side it has to be done on their side and i did not even apply or approve. I know it does not sound like much bit if i could have afford it i would apply.!!!!!!!