"harassment doesn't stop"

This company purely harasses people for money they do NOT owe. FNB does not debit people at the end of January on personal loans ( you can google the January break). anyways, i have told this company off for this already, that they need to start doing their own research before calling clients asking for money. i got an email reply that i was infact correct but no apology for the harassment or the mistake they made. we are now in March and I know for a fact i am not outstanding on any payments yet they still keep calling my work number. This company needs to close down if they don't know what they are doing.