Who called from 3123768003

i've been get multiple calls from this number day and night for the past couple of days, but they never leave a voicemail. i have no idea who this is.

Same here, I guess it's a Chicago based TMobile cust. service. I know they want money from me...

It is TMobile calling.  I call them back and it goes into a tmobile auto attendant.  This is probably a robocall for late due $ before they shut you off.  I am 1 pay cycle behind.

Caller called and didn't leave a message.  It was T-Mobile