Contact AT&T to see if they offer this. As far as I know (and I could
be misinformed), your AT&T will automatically renew every month unless
you let AT&T know you do not want it to renew. I believe this can be
done via AT&T website or phone call to Customer Service. I suggest
you contact AT&T as soon as possible to get it straightened out rather
than wait until right before your trip when you will already have enough
to deal with.