You are not going to be able to cancel it either if it falls outside the 120 days. Expired is expired. The reality is that the prices are contingent in part of length of stay and 120 costs less than 1 year and they won't create 1 year for free. Best option might be to buy a cheap R/T and toss the return portion. The OP didn't say where they are now or going to/from (they so rarely add this detail...) so it is specualtive as to the advantage of that but doubtlessly less than one-way.