A message that says "I am interested in your item, kindly text me" is generally the start of a scam where the scammer winds up sending a phony PayPal email that makes it look like the seller has received a payment when none has actually been received. Scammers like to target new sellers, particularly those selling expensive items.
Similarly, any potential buyer that wants to pay more than your buy-it-now price or asks you to purchase a gift card for any reason is trying to scam you. eBay has no way for a seller to add the extra cost to the transaction, so that should tell you that the buyer has no intention of paying you through eBay (or at all).
Sending contact information (text or email) prior to a transaction is a violation of eBay policy; this policy is designed to protect honest buyers and sellers from this sort of thing, and to prevent off-eBay sales.
Ignore anyone that wants to communicate outside of eBay prior to a transaction payment. eBay will likely close the scammer's account eventually; unfortunately the scammer will simply open another account and continue sending such messages.
As a seller you should always check your PayPal account directly (not following a link in an email) to see if you have actually been paid prior to shipping. If an actual buyer does not send an actual payment, file an unpaid item dispute and go through that process to get your fees back and to give the "buyer" a strike -- and set your buying requirement to reject bids from users with two or more strikes.
