Do you believe in promotions that give gifts for recharging phone credits?

I was just playing on my phone when China Unicom called me and said there's a promotion offering gifts for recharging, and I can participate at any offline store. I asked if county-level stores are eligible, and she said yes. Then I asked when the promotion ends. She said as long as I participate by the end of the month, it's fine.
By the way, have you ever participated in similar promotions? What kind of gifts do they usually give? I hope they won't ask me to upgrade my plan again at the store. My current plan costs 39 yuan and only 468 yuan a year, which I think is quite cost-effective. If I upgrade, I might stop using China Unicom because I only choose it because it's cheap.