Growing up — and out of your family's cell-phone plan

Q. My parents asked me to start paying for my share of our family wireless plan. Should I get my own before heading back to school?

A. Going on your own can save real money, but you may cost your parents some at the same time. That’s because the shared plans offered by all four nationwide wireless carriers — along with many “mobile virtual network operator” firms reselling their networks — really function as customer-retention tools.

That is, while they offer substantial savings for putting multiple lines on one bill, having so many services on one account complicates taking some of that business elsewhere. And subtracting a line from a shared plan will increase cost for people left on it.

Consider what unlimited (really, unmetered) data plans cost per line (including discounts for automatic payments) at the big four carriers:

• At AT&T, you pay $46.25 a line for four lines, $55 a line for three, and $72.50 for two.
• Sprint’s current promotion has you paying $22.50 for each of four lines, $30 for each of three and $45 for each of two.
• T-Mobile charges $40 a line for four, $47 apiece for three lines, and $50 each for two. All cases come with only standard-definition streaming video and mobile hotspot use capped at 3G speeds.
• Verizon Wireless asks $45 a line for four lines, $54 each for three lines, and $70 a pop for two.

Taking yourself off your parents’ plan may liberate them to switch to a cheaper plan. If they’re okay with paying a little more for not having to worry about your own use, you can start looking for cheaper options on your own.

Related:When our smartphones leave us out of touch

In a WiFi-dense environment like a college campus, the biggest savings will come from a WiFi-first service that routes calls and texts over that wireless network instead of the cellular service (usually, AT&T or T-Mobile) it resells.

One service that topped recent readers-choice surveys at Consumer Reports and PCMag was Project Fi, the service Google launched in 2015. Unlimited calling and texting via Sprint, T-Mobile and U.S. Cellular costs $20 a month, after which data runs $10 a gigabyte (with whatever fraction of a gig you don’t use credited back after each month).

The catch: Project Fi only supports Google’s Nexus and Pixel phones, of which just the Pixel and Pixel XL are left on sale.

Another WiFi-first service, Republic Wireless, did well in CR’s survey and is even cheaper than Fi. Unlimited calling and texting run $15 a month (with coverage from Sprint and T-Mobile), and adding 1 GB of data raises the rate to just $20. But Republic is also picky about phones, with support confined to a set of recent Android models.

More:Zing! Sprint opens 'Twice the Price' store next to Verizon retailer

More:Cellphone plans for seniors offer more service, lighter data

A more traditional reseller, Consumer Cellular, also earned high ratings in those reader surveys. This reseller of AT&T and T-Mobile lets you mix voice and text-plus-data plans to match your usage. For example, 250 minutes of calls, unlimited texting and 1.5 GB of data would run $45. And it’s far more accepting of hardware, so you can bring your unlocked iPhone there or buy one from the firm.

Don’t rule out the big four carriers either; you may find that your school has a discount program offering substantial savings unavailable on your parents’ plan.

Whatever you do and whatever service you wind up on, please remember to use it to call your folks at least once a week, okay?

Rob Pegoraro is a tech writer based out of Washington, D.C. To submit a tech question, e-mail Rob at rob@robpegoraro.com. Follow him on Twitter attwitter.com/robpegoraro