“充话费” means “to prepay mobile service fees,” and “送的” refers to “a free gift.” Because competition is fierce in the Chinese telecom service market, some mobile carriers offer prepaid services that come with a phone as a free gift. That is, if the user deposits a certain amount of money as prepaid fees, they can get a free phone. Chinese netizens use this term to mean “a free gift, something thought as not valuable and therefore not treasured.”
Jīntiān xuéxiào zǔzhī qù dòngwùyuán wán，nǐ gěi háizi zhǔnbèi le shénme biàndānghé？
The school has planned an outing to the zoo today. What lunchbox have you prepared for your kid?
Wǒ gěi tā mǎile yīdài miànbāo，yīhé niúnǎi。
I’ve got him some bread and a box of milk.
Shūcài shuǐguǒ dōu méiyǒu，nǐ zhè háizi shì chōnghuàfèi sòngde ma？
You haven’t prepared any vegetables or fruit. Is your kid a free gift from the mobile carrier?