As it gets chillier outside and the Hocus Pocus marathons begin, October is definitely a time when you want reliable internet. Right now, if you bundle a phone line with T-Mobile's 5G home internet, you'll save $20 per month -- and if you're a new customer, you could also get a $100 Mastercard gift card, too. It seems like every time I see a commercial, it's for a rival internet or phone service provider, trying to prove why their rates, coverage, or reception is the best. With all of the conflicting info, color-coded maps, and endless fine print next to asterisks, it can be nearly impossible to figure out if an internet and phone bundle is right for your needs and budget. I spent nearly half an hour on the phone with a T-Mobile rep to get all the ins and outs of their $20-off 5G home internet and phone line bundle, so you can have as much information as possible on this deal. Here's what to know, and how to sign up. Also: What is 5G home internet? How to take advantage of this T-Mobile deal First, head to the T-Mobile website and enter your address to see if you're eligible for the 5G home internet service (note that the savings will appear at checkout, not on the initial web page). If your address is eligible, you'll be taken to a screen with numerous home internet plans ranging from $55-$75 per month. Here's where the savings start. While the website says it costs $55 per month for Rely 5G home internet, T-Mobile will actually knock off $5 per month for all of its plans (across phone and internet) when you enroll in auto-pay, which brings the new starting cost to $50. If you sign up for the Rely plan, you're also eligible for a $100 rebate via a prepaid Mastercard gift card after 14 weeks. Also: Are you paying more for cable and internet? It's bad all over Once you add a phone line to the 5G Rely home internet, you'll get a discount of $15 off per month for internet, bringing the cost from $55 to $35 when paired with the autopay deduction. However, your bill won't be as low as $35, because the promotion depends on your adding at least one phone line. T-Mobile has three phone plans to choose from: the Essentials plan, the Experience More plan, and the Experience Beyond plan. Also: T-Mobile's Starlink just added WhatsApp, Google Maps, and more The Essentials plan is $65 per month per phone line ($60 with autopay), and offers unlimited calls and text with 50GB of data per month. The Experience More plan is $90/month per phone line ($85 with autopay), and offers unlimited high-speed data and 60GB of mobile hotspot data (including 15GB in Canada and Mexico), phone upgrades every two years, and included accounts for Netflix and Apple TV+. The Experience Beyond plan is $105/month per phone line ($100 with autopay), and offers unlimited mobile hotspot usage, 30GB of high-speed data in Canada and Mexico, upgrades every year, the ability to add a watch or tablet line for $5/month, T-Satellite, and accounts for Netflix, Apple TV+, and Hulu. It's worth noting that all streaming service accounts would be at the lowest tier (meaning with ads), but you'll only need to pay the difference if you choose to upgrade to a more expensive plan. Also: The best live TV streaming services available ZDNET T-Mobile's 5G Rely home internet has a typical download speed of 133-415 Mbps, a typical upload speed of 12-55 Mbps, and a typical latency of 16-28 ms according to their website, which isn't too shabby, especially at $30/month. Of course, this deal sounds a bit misleading, because you can't get $20 off the monthly internet price without paying at least $60 in addition per phone line (bringing the lowest possible monthly total to $90), but it's still a sizable discount. Two more pieces of fine print: There's a one-time device connection charge of $35 for the home internet service (even when you install it yourself), though installation is apparently super easy, and can usually be completed within 15 minutes. All of their internet bundles come with a 5-year price guarantee, meaning that the price won't increase for at least five years. Looking for the next best product? Get expert reviews and editor favorites with ZDNET Recommends. How I rated this deal While it's a bit more complicated than saying that T-Mobile is offering 5G home internet for $30/month, $20 off is still a sizable discount. I didn't rate this deal as exceptionally exciting, mostly due to the fact that you'll have to spend at least 3x the alleged discounted price to take advantage of the discount. When will this deal expire? We're not sure how long this promotion will last, though the T-Mobile rep I spoke to suggested that you'll probably have some time to consider if this deal is right for you and your budget. Deals are subject to sell out or expire anytime, though ZDNET remains committed to finding, sharing, and updating the best product deals for you to score the best savings. Our team of experts regularly checks in on the deals we share to ensure they are still live and obtainable. We're sorry if you've missed out on this deal, but don't fret -- we're constantly finding new chances to save and sharing them with you at ZDNET.com. Show more How do we rate deals at ZDNET? We aim to deliver the most accurate advice to help you shop smarter. 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