"I followed up with a call today and I was advised that they will not waive the $200 early termination fee as the account was in my name, not his."
The woman lodged a complaint with Telecommunications Dispute Resolution.
She said the experience was "a shocking display of an incompassionate organisation with extremely poor support staff [and] a ridiculous process of registering complaints.
"The service I received was disgusting."
The Herald contacted Slingshot today and was told that earlier in the day, the company had waived the fee.
"Late this morning we waived the termination fee and outstanding fees on the account," said customer operations general manager Catherine Adams.
"We, of course, should have done this earlier in the morning when [the woman] initially spoke with us.
"The mistake was human error and against our policy. We have spoken to the staff members concerned and have extended a further apology to [the woman]."