T-Mobile Get a 4th line FREE. NEW PROMO For existing family plan or new customers.

T-Mobile has new promotion slightly different from previous which require add 3rd line and get 4th free.

Also, if you never had a free line then you may be able to add free line. Just call 611.
Costco wireless should have this just ask rep. Family plan most likely need to add only one line if they have at least 3 line. Will add more details as available.

$140/mo. Taxes & fees included 4 lines. Price with AutoPay and 4th line on us.

Full terms shows as below.
Get a 4th line FREE.

Via monthly bill credits. Limited-time offer; subject to change. For existing family plan or new customers. Qualifying credit and family plan required. Credits may take up to 2 bill cycles; credits will stop if you cancel any lines. Limit 1 offer per account.

https://www.t-mobile.com/cell-pho...53URT18881

https://www.t-mobile.com/offers/deals-hub

Choose your lines. See what you'll pay.

Select how many lines you need to see what your monthly rate will be. Taxes and fees are included, so you'll never pay a penny more for Magenta.

4th Line Free: Via monthly bill credits. Limited-time offer; subject to change. For existing family plan or new customers. Qualifying credit and family plan required. Credits may take up to 2 bill cycles; credits will stop if you cancel any lines. Limit 1 offer per account. Magenta General Terms: Credit approval, deposit, $10 SIM card, and, in stores & on customer service calls, $20 assisted or upgrade support charge may be required. Capable device required for some features. U.S. roaming and on-network data allotments differ: includes 200MB roaming. Unlimited talk & text features for direct communications between 2 people; others (e.g., conference & chat lines, etc.) may cost extra. Unlimited high-speed data US only. In Canada/Mexico, up to 5GB high-speed data then unlimited at up to 128kbps. Not available for hotspots and some other data-first devices. Video streams at up to 1.5Mbps. Optimization may affect speed of video downloads; does not apply to video uploads. For best performance, leave any video streaming applications at their default automatic resolution setting. Netflix: Offer subject to change. Receive Netflix Basic (1-screen, up to a $8.99/mo. value) while you maintain 2+ qual'g Magenta lines in good standing. Value may be applied to different Netflix streaming plans. Not redeemable or refundable for cash. Cancel Netflix anytime. Netflix Terms of Use apply: www.netflix.com/termsofuse. 1 offer per T‑Mobile account; may take 1-2 bill cycles. See t‑mobile.com/netflix for add'l info. Like all plans, features may change or be discontinued at any time; see T‑Mobile Terms and Conditions at T‑Mobile.com for details. Tethering: 3GB high-speed data then unlimited on our network at max 3G speeds. For the small fraction of customers using >50GB/mo., primary data usage must be on smartphone or tablet. Smartphone usage is prioritized over Mobile Hotspot (tethering) usage, which may result in higher speeds for data used on smartphone. AutoPay Pricing for lines 1-8. Without AutoPay, $5 more/line. May not be reflected on 1st bill. Int'l Roaming: Usage may be taxed in some countries. Calls from Simple Global countries, including over Wi-Fi, are $.25/min. (no charge for Wi-Fi calls to US, Mexico and Canada). Standard speeds approx. 128Kbps without PlusUp; with PlusUp approx. 256 Kbps. Not for extended international use; you must reside in the U.S. and primary usage must occur on our network. Device must register on our network before international use. Service may be terminated or restricted for excessive roaming. Coverage not available in some areas; we are not responsible for our partners' networks. Gogo: on U.S.-based airlines; Wi-Fi Calling functionality, valid e911 address, & 1 prior Wi-Fi call w/ current SIM card req'd for messaging. Stateside Int'l Talk: Calls must originate on T‑Mobile's U.S. network or in Canada/Mexico. Rates and included countries vary and may change. Coverage not available in some areas. Network Management: Service may be slowed, suspended, terminated, or restricted for misuse, abnormal use, interference with our network or ability to provide quality service to other users, or significant roaming. During congestion the small fraction of customers using >50GB/mo. may notice reduced speeds until next bill cycle due to data prioritization. On-device usage is prioritized over tethering usage, which may result in higher speeds for data used on device. See T‑Mobile.com/OpenInternet for details. See Terms and Conditions (including arbitration provision) at www.T‑Mobile.com for additional information.