I did that and it was almost $140You might be surprised. Go check "manage your plan/wireless" like Illini Al said.
Ignore the 5 lines part.
https://www.att.com/plans/unlimited-data-plans/?source=EC1NvIDES0000000P&tfn=wireless&WT.srch=1&wtExtndSource=+att++unlimited&gclsrc=aw.ds&&gclid=EAIaIQobChMIo6-XzJK17AIVxsDACh0BlQpgEAAYASAAEgKwUPD_BwE&gclsrc=aw.ds