To be specific, 3 MONTHS according to https://www.globe.com.ph/help/data-and-network/gosurf-and-spotify/gosurf-spotify
"If you're a Postpaid customer, however, you can get 3 months free Spotify Premium as long as you're registered to GoSURF. If you unsubscribe from GoSURF, your Spotify Premium subscription also ends. The 3-month free trial period starts from the time your register to GoSURF.
At the end of the 3- month free trial period, your free Spotify Premium will auto renew to the Spotify stand-alone promo (Spotify only) worth P299 for one month. You will be notified before the end of your free trial to remind you that Spotify will auto renew to the chargeable promo P299/30 days unless you unsubscribe.
Note: You must unsubscribe from Spotify before the end of the trial period if you don't want to pay for the Spotify plan by texting SPOTIFY STOP to 8888."