In a bid to lure customers from Verizon Wireless, Sprint is now offering a free year of its Unlimited service for anyone who makes the switch. But with all such “free” offers, there are costs involved.

The biggest catch for this promotion, which ends June 30, may be the fact that Verizon customers would need to bring their current phone with them. That means that if you’re currently paying a monthly fee to Verizon for your device, you’ll need to pay off the remainder of that phone to make the switch to Sprint.

So imagine you just got an iPhone 7 three months ago through Verizon. Switching now to Sprint would mean paying more than $567 (21 months x $27.08/month).

Conversely, if you’ve got an older device that you’ve paid off already, you won’t be able to ask for an upgrade through Sprint until Oct. 2017.

If your payoff amount for your current device is low and/or you’re fine with waiting until the fall to get a new phone, then this may not be an issue, especially since a year of $0 in talk/text/data charges from Sprint would save you more than $900 over the comparable Verizon plan (currently $80/month plus phone charges for a single device).

New Sprint customers won’t have to pay the usual $30 activation fee or pay for unlimited data, talk, text, and 10GB of hotspot data per line, but there are a few charges involved nonetheless:

• Customers will have to pay $2.99 for a SIM card, plus $10 in shipping and handling, and tax.

• A standard $1.99 admin fee, $0.40 regulatory fee, and other taxes and fees apply.

• Though the usual $30 activation fee will be waived, it will appear on your first bill, and you’ll be credited within two months.

After July 31, 2018, customers will pay $60/month for one line, $40/month for two lines, or $30/month for three to five lines. If you cancel AutoPay, add $5/month/line.

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