VODACOM CANNOT DO THE SIM SWAP BECAUSE THE SIM IS IN USE!

I am extremely disappointed with the service that i got from vodacom. I lost my contract phone last week. i immediately called vodacom to lock both the phone and the simcard. i subsequently requested to do a simswap but i am told that i can't do it because the sim card is apparently in use. i dont even understand how is that possible because they have locked it, how can it be in use whilst i as a payer cant use it? . i have to spend another week without the simcard because i have to go the branch, that is very far from me but yet the money is being debited without fail.