In addition to the advice you have already been given, whatever you do, don't list items such as mobile phones on eBay again. As you have unfortunately found out the hard way, mobile phones are scammer magnets.
Another factor which has played a part in this scenario is the fact that you are a new seller to eBay. Scammers tend to target new sellers as they see them as having very little experience of selling on the platform and therefore see them as easy targets. Combine this with the fact that you advertised a scammer magnet for sale and you unfortunately set yourself up for the scam.
If you have not already done so by the time you read this response add the buyer's User ID to your Blocked Bidders List. Due to the fact that you have recently been in a transaction with this buyer the blocks will take longer to kick in than would otherwise have been the case, but once they do he/she will not be able to purchase anything else that you advertise for sale and cause you any further aggravations.
Finally, when adding the buyer to your Blocked Bidders List make sure that you tick the box next to the sentence that reads "Don't Allow Blocked Buyers To Contact Me." Once you have done this not only will it prevent anybody on your Blocked Bidders List from being able to contact you, but you will not have to keep on activating it every time you add another person to your Blocked Bidders List, as once you have activate the "Don't Allow Blocked Buyers To Contact Me" option it will remain active forever unless for some reason you change your mind at some point and decide to deactivate it.
