Help please with moible phone account

I have an iPhone and bought a pre-paid SIM from Orange. When I buy credit, it seems to expire if not used, and last week, I bought credit in the local tabac but the credit he sold me was credit only so can't send texts. I have gone to Orange website, but my French is obviously not up to the task, because I can't understand the various offers, and can't find out how to pay and top up on line. I would prefer an account which is what I am used to. Any suggestions or advice would be warmly welcomed. Oh, and am not wedded to the idea of Orange.

Thank you very much Christa. Successfully topped up on line this morning.