Should i call after a job interview?

i interviewed for a part-time teller position at a bank on monday, the 20th. they said they might still be interviewing this week, and if they were, they'd call and let me know. they also said to expect a call this week if they're hiring me or whatever. well, they havent called.. and it seems like either way they would have on monday. should i call them? and if i do, what do i say? i wanna keep it short and simple. i'm kinda verryyy nervous to call them though, so i was thinking i could just send a thank you letter, but i don't know because its only a part time job, and it might be too late, its been a week. plus, this is a small town and that seems more for like a bigger town... idk what to do. should i call or just wait for them to or what?