Some old metal handsets are now deemed to be "classics" and even "antiques", which means they are selling for hundreds of pounds, report Wales Online.
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The amount of money to be made from old mobiles will depend on the make and model, but research from talkmobile has found that 56.8% of people have an old phone lying around.
According to the experts, you might find a phone worth a small fortune, as some retro handsets are now classed as modern antiques with collectors willing to pay handsomely for them.
But if you have a mobile phone that is not worth trying to sell on eBay then there are number of charities that will recycle old phones.
For example Oxfam will use the cash from recycling an old mobile to buy vital kit, such as water tanks, wells, tools, seeds, school books.
Mobile phone expert Ben Wood, from CCS Insight, who has a collection of nearly 1000 mobile phones from the last 30 years said: "We all remember our first mobile phones, whether it was the iconic brick-sized Motorola DynaTAC used by Gordon Gekko in Wall Street, a Samsung that flipped open, or the noughties manufacturer of choice, Nokia.
"It's now over 30 years since the first mobile phone became commercially available and a whole generation of people have owned a host of different handsets over the years.
"Finding an old handset in the back of a drawer can be an evocative experience. People tend to remember the phone they had during significant periods in their lives, such as a certain job or a particularly memorable holiday. It's interesting that a piece of technology can induce sentimental feelings in many people."
The study showed our most affectionate memories are for the humble Nokia 3310 and 3390 models.
The most popular phone of the late 90's and early 00's featured pioneering elements such as an inbuilt aerial, exchangeable cases, text messaging and the addictive game Snake.
"It's no surprise people are nostalgic about their Nokias," says Ben. "The brand was a real game changer back in the nineties and Nokia worked extremely hard to make the mobile phone accessible to everyone.
"Nokia phones were affordable, robust and reliable, and unlike most smartphones of today, sometimes only needed charging once a week. Thanks to Nokia the mobile phone became the most prolific consumer electronics device on the planet."