These texts are not from Best Buy. The are from scammers pretending to be from Best Buy. They are faking their phone numbers, pretending to call from hundreds of number. The callers are using a robo-dialer to call every number in the US.
If you reply they will ask you for a credit card number or bank account number to pay for shipping and handling and insurance. They will spend all of the money in the account. They will never send you a gift card. If you visit the website in the message it will download spyware and viruses and heaven knows what else.
Delete the message. Do not reply to it. Do not visit the website in the message.
This thread
http://800notes.com/forum/ta-46d2613af143609- ... t-buy-gift-card
has over 3000 posts, people like you who got the e-mail and people like me telling them it’s a scam.