A tried-and-true strategy by which businesses are able to attract new customers is by offering promotional (or limited-time) pricing on their products or services. But anyone who’s ever signed on the dotted line will certainly warn you in advance: once those 12- or 24-months come to pass, your bill is bound to get a bit messy.

Such is about to become the case, unfortunately, for a number of Sprint customers, according to a statement released this week by the nation’s fourth-largest telecom-giant. Namely, Sprint’s two major promotions: “Unlimited Freedom” and “50% OFF” are scheduled to end as early as mid-January, 2018, FierceWireless reports.

“Customers on Unlimited Freedom and 50% off were informed when they signed up with Sprint that the plans were introductory pricing and would increase in price at a future date,” Sprint’s Kathleen Dunleavy wrote in response to FierceWireless’ questions, adding that the company went so far as to reiterate these expiration dates to customers via multiple, subsequent communications.

“The great news is these customers are still paying less for their service compared to other major carriers. Plus, Sprint now provides unlimited customers Hulu at no additional cost. Sprint is very competitively priced and customers can call Sprint at 1-800-SPRINT1 if they have additional questions.”

Initially unveiled back in November, 2015, Sprint’s “50% off” promotion attempted to lure cost-cutters to its network by promising to “cut 50% off the price of most” rivaling plans offered by T-Mobile, Verizon, and AT&T.

Sprint maintains it was clear, at the time, that new activations registered between Nov. 20, 2015, and Jan. 7, 2016, would enjoy the 50% off promo pricing until at least January 8, 2018. Dunleavy pointed out, however, that customers’ individual expiration dates are dependent on when they initially signed up for the promotion.

Same rules apply to the carrier’s “Unlimited Freedom” promotion, which offered customers up to five lines of unlimited talk, text, and data for [roughly] $20 per line. After January 31, 2018, however, “customers pay the additional $30 per month for those lines,” Sprint said.

Wave7 — a market research firm who closely tracks wireless carrier pricing offers relative to migration among post-paid customers — was first to shed light on the impending shut-off of Sprint’s promotions.

They added that the carrier is expected to begin contacting “roughly 300,000 customers” regarding the January, 31 expiration soon, while those who signed on to either promotion at a later date should be contacted as their expiration date approaches.

We can’t even begin to fathom what kind of impact this will have on Sprint’s bottom-line, but according to multiple Wall Street analysts who’ve already chimed in on the news, Sprint could be looking at a slightly higher churn (or post-paid subscriber defection rate) in the fiscal Q1 and Q2 of 2018.