Can I put my account in Stand By with no pay (I mean for ie, use and pay just for 6 months per year)

The only payment option currently is through recurring, automatic payments via credit card, with no means to pause payment while keeping your account and service active.

I think the best you can do is select a plan with no data, no text and no minutes.  It will still have a per-month cost, but you could change your plan in the payment cycle before you need voice / text / data to have it enabled on the next month.  Alternatively, you should be able to select various add ons as needed.