You can send them a message through Facebook or Twitter too.

Just a note. The seasonal hold is count as a plan change. If you have a promotional plan, you wont be able to get it back when you came back.  You need to pick a plan from in-market plan.

Keep in mind also if you need to do banking or anytging that requires 2FA,you won't be able to receive any codes. There's been a few people here lately asking to switch back to a plan to be able to receive 2FA codes.

Your best bet is to change to the $15 starter plan.  This way you can at least receive texts.  Just watch out for roaming by removing your sim and only plugging it in when you need to receive a text