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If its been that long since the number was used @Rb9 the number will be gone and impossible to get back after almost 3 years of non use.
There are not an infinite number of mobile telephone numbers available and networks have to disconnect and reuse the numbers.it is an Ofcom ruling that all PAYG numbers have to be in use, otherwise there would be thousands and thousands of unused numbers.
You should have received a text notification after 90 days to remind you to top up of make a chargeable connection, this would have been followed up with a further message 45 days later, and an additional message 45 days after that, and you would have needed to take action to prevent disconnection before the final cut off period. Networks don't disconnect a number without prior warning to the phone.
You won't be able to get the number back, it's long gone, and may have been ported out to another network many times. You either use or lose a PAYG number.
I would also suggest you use the forum search facility there are plenty of previous threads asking the same question.
If you ring the number does it ring out or is it dead ?
If it's dead then it's probably been quarantined for the number to be re issued out at a later date due to it not being used within a 180 day timeframe
A Payg account can be deactivated if no activity such as calls , texts , data usage or top up hasn't been made within a 180 day period.
Vodafone set out in their Terms and Conditions.
Once quarantined a person usually only has 90 days to get it back.
Use Vodafone Live Chat or contact the Vodafone Social Media Teams via Facebook Messenger or Twitter DM Contact-us-for-account-specific-queries and they'll certainly see if the number can be returned to you.
It costs nothing to ask the question
We are fellow customers here so cannot say whether they can or not.
I wish you all the best.
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