FOR TWO YEARS/Per month

Sir,I want to purchase VPN-Avast SecureLine with 2 yrs subscription for 1 PC + 1 yr for my Android .
Should pay the whole amount at a time or I might pay per month as installments ? It will be very helpful to me if you allow me to pay per month ,if needed auto pay method . Kindly confirm me via my email < spdas4g@gmail.com >.
Yours faithfully , SIBAPRASAD DAS.

http://www.avast.com/nl-nl/secureline-vpn