Future Nine vs Aircall

I used future nine for more than five years. At the beginning, their service and price are pretty good. But recently, I noticed that there is a lot of small amount charge deducted from my account. For example, I deposit $15 in my account, after one week, there is only $14.3 left on my account. I sent email asked the reason and there is no response from them. I could not find the explanation for these charge in the invoice. And from the invoice, you could not find these deduction. My friends also complained that sometime when they call me, they received a voice message told them the call could not go through. They have to call my cell phone and found there is no ring in my home phone. There is no response from their customer support after I sent email to them ask the reason. Finally, I decided to cancel the service from future nine after being their customer for more than 5 years. I received a message from them and told me there is $15 cancellation fee and the remain balance in my account is nonrefundable. After I canceled the service, I still received the billing that charge for the future service.