I sent my phone in and when they received it I was told I'd receive payment within 5 working days. On the 5th working day I received ful payment that they told mee.

It's a company (legitimate, it seems) apparently trading on the barely-ethical premise that users can be cajoled into accepting below-market prices for their property once the property has already changed hands. Online reviews suggest that they systematically revise their quotes without rationale by a substantial percentage, offer little or no explanation or recourse, and offer a very poor user experience, per ratings.