CHICAGO (CBS) — A Chicago couple was at their wits trying to unlock their phones, forced to endure a months-long runaround after switching cellular carriers.

Gita and Ramesh Rupani were AT&T customers for 15 years, then decided to change carriers.

“We just didn’t realize that it would be such a problem,” Gita said.

Three out of their five phones were locked, and couldn’t make the switch.

“When you buy a phone from a carrier, there is software that they put into that device that keeps it from moving to another carrier,” said CNET executive editor Roger Cheng. “The argument there is that this is a way to prevent theft.”

Cheng said, if a customer outright owns their device, “unlocking a phone is actually the carrier’s responsibility.”

“I decided, okay, I have to get to the bottom of it, and if they say no, that’s when we’ll throw these phones away,” Gita said.

The couple first tried to unlock their phones at an AT&T store while in New Jersey. No dice, so they called AT&T.

“They wouldn’t unlock, saying that that’s not their phone,” Gita said.

Ramesh said the couple still had the bill from the last installment they paid on the phones in August 2017. Proof in hand, Gita then tried an AT&T store in Chicago, only to be directed to the Apple Store, which she also visited.

“It’s been over a period of about three months,” Gita said.

AT&T even suggested the Rupanis pay someone to unlock phones they already own.

“If they are directing you to Apple, or a third party vendor, they’re definitely in the wrong,” Cheng said.

Cheng said he would never recommend using a third-party service to unlock your phone.

“There could be a cybersecurity issue concern. It’s more they’re going to inevitably charge you for this, and it’s not something you need to pay for,” he added.

Gita said the most frustrating part was having phones they paid off, but which were rendered useless when they changed carriers.

After CBS 2 got involved, AT&T said it contacted the Rupanis, and helped unlock the phones.