When the US firm announced it had been slowing down iPhones in order to "preserve battery life" in December last year, it apologised for not telling people sooner.

Facing a consumer backlash, it promised owners of the iPhone 6 and more modern models a discounted or free battery replacement.

It said: "We are able to do the work we love only because of your faith and support - and we will never forget that or take it for granted."

But since then, some Watchdog viewers have told the programme that their faith in the company has been seriously shaken after trying to take Apple up on its offer.

Apple demanded that some customers pay 10 times the sum it referred to in its apology.

The company told customers this was because of existing damage to their phones that would impair the replacement of the batteries.

But Watchdog's investigation found that this is not always the case.

Josh Landsburgh sent his phone off to have the battery replaced in February.

Two days later, he received an email from Apple pointing out a small dent to the edge of the phone, and quoting a cost of over £200 before it would make good on its battery promise.

A furious Josh had the phone returned from Apple. He had the battery replaced without an issue at a local repair shop - which meant he voided his Apple warranty.

"They're trying to regain trust and they come back to you with, 'Give us more money than you were planning to initially.' I think it's just shocking, they've got enough money, they're Apple," he told the BBC.

David Bowler also contacted Watchdog.

 Watchdog’s Nikki Fox meets David Bowler, whose phone Apple also claimed had “extra damage”

His phone was in perfect condition, but needed the battery replacing. This time, with no apparent damage outside, Apple told David there was damage inside the phone.

The firm said the front microphone and speaker were faulty, quoting over £250 to resolve the issue.

But David is adamant these components were working perfectly. He asked for his phone back, and Watchdog took his device to a mobile repair specialist.

It told the programme: "Obviously these things are working; they shouldn't say that they are faulty."

The specialist also replaced the battery with no issues, something Apple had refused to do without fixing the microphone and speaker first.

So, is Apple profiting from saying sorry?

Watchdog took David’s phone to a specialist to have the battery replaced

Apple's repair website does state that "if your iPhone has any damage that impairs the replacement of the battery, such as a cracked screen, that issue will need to be resolved prior to the battery replacement".

It also offers a fresh 90-day warranty on any device it has serviced, even if the original guarantee had long expired.

Furthermore, some Apple customer service representatives - contacted via webchat - said the firm made clear in its warranty that "any and all damage" must be repaired first before battery replacement.

But neither Watchdog nor dispute resolution lawyer Matthew Purcell, of Sanders Law, could find any mention of this requirement.

Mr Purcell told the programme: "I think consumers are getting annoyed because at a time when Apple should be rebuilding trust, it seems like they're putting barriers in the way of people getting their phones repaired."

Apple sent the BBC the following response:

"When it comes to iPhone battery replacement, if your iPhone has any damage that impairs the replacement of the battery, such as a cracked screen, that issue will need to be resolved prior to the battery replacement. In some cases, there may be a cost associated with the repair."

It has referred customers to its website for more information.