If you sign up with MileagePlus Mobile Offers by October 21, 2012, you can get 500 free United miles. MileagePlus Mobile Offers will send you mile-earning opportunities by text message (up to 3 per week) on your mobile device when you use your registered Visa card.

All you need for this MileagePlus Mobile Offers Promo is your MileagePlus membership number, your eligible Visa card, and your mobile phone number. Once you register, your 500 bonus miles will be posted after 6-8 weeks. You can cancel the service at any time, but I would wait until after the miles post.

“REGISTER FOR MILEAGEPLUS MOBILE OFFERS AND GET 500 BONUS AWARD MILES. Receive mile-earning opportunities faster by text message on your mobile device when you use your registered Visa® card. Getting started is easy. All you need is your MileagePlus membership number, your eligible Visa card and your mobile phone number.Register up to three eligible Visa cards for special mile-earning opportunities. You’ll receive up to three MileagePlus offers by text each week when you use any of your registered Visa cards.”

To really take advantage of this offer, sign up with your Chase United MileagePlus Explorer Card. This Visa gives you up to 40,000 bonus miles with loaded benefits, including waived fee bag check-in for all card members + one guest, priority boarding, and free access to the United Club – a $100 value. There is no annual fee for the first year and $95 thereafter.