Question

You're locked in with us.
What is meaning of locked in in this sentence.
IS this mean "you are with us"?

Answer 1

It could mean you have a contract that you can't break. Example: if you signed to Verizon for a year and wanted to switch to AT&T, Verizon could say "You're locked in with us for the rest of the year", so you would still have to pay for the rest of that year.