Hi, thank you for supporting our service.
 
Here is a short summary:

1. You only paid for February and March (2 months), there is no billing mistake or extra charges for 3rd month.
2. It's common that subscription extends automatically. Your refunding request for March is not well grounded.
3. However, we can refund you 0.0075 BTC as a gesture of good will should you wish so.
4. Alternatively, if a bimonthly plan with a lower fee was your intention, we can change your plan to bimonthly retroactively.

Now in more details:

I confirm that you chose a monthly plan and payed an amount of two monthly fees on Feb 10. Your subscription was activated on Feb 10 and for 2 months there were enough balance so the service continued till Apr 10.
 
Now your balance is -0.0075 because there's one outstanding invoice. If you change your plan the invoice for 0.0075 will be cancelled and invoice for your new plan will be issued.

If you send 0.0075 BTC, the service will be extended by one month since the moment of payment, not since the moment of invoice.

So as you can see there is no an error on our side.  There are no any extra charges of your account. You were only charged 0.0075 BTC 2 times, not 3 times.

As for refunding request for March service you didn't intend to receive.

If you add funds to your mobile phone, there's no way to withdraw, and they are consumed over time if your tariff plan includes a monthly payment even if you don't intend to talk. If you buy a larger scratch card to add funds than you intended, there's no way to get a change.

Bitcoin Analytics uses the same billing model.

You should have either send 0.0075 or choose a bimonthly plan of  0.00125 per month. Your demand to get a refund for April is not well grounded.

If you agree with above, we can fix your plan selection mistake and charge you 0.0125 for March and April according to bimonthly plan instead of 0.0150.
 
If you insist on a refund, since it's the first such request, we are sure it's not fraudulent, and can refund. Please send us your bitcoin address to return the money to. Send a PM to either nimnul or genuise if you consider it sensitive.

with all respect,
Andy and Evgeniy
bitcoin-analytics.com