The big four major cellular providers see dollar signs every time a new iPhone is released to the public. Each new iteration of the immensely popular smartphone is an opportunity to keep a lot of existing subscribers and to win over some new ones as well.

This is done through each of the companies offering trade-in programs that give consumers looking to get rid of their obsolete iPhone in favor of the new iPhone 6 or iPhone 6 plus.  While services like Gazelle and Nextworth have similar practices, the trade-in deals provided by these companies is much more valuable, which should entice more consumers in their decisions.

Verizon Wireless

Verizon will offer guaranteed pricing through store credit or gift cards for anyone who gets rid of their iPhone to get an iPhone 6 or 6 plus. The gift cards will be for $200 for an iPhone 4, 4S, 5 or 5C. Those choosing to trade in an iPhone 5S will get a $300 gift card.  The offer runs until Sept. 30. To take advantage of the offer, customers must  turn their phones into a Verizon store or complete a request online and then send in their receipt and get their gift card in return.

To make it even more interesting, it does not matter if the iPhone is from Verizon or another carrier, nor does it matter if the customer is already a part of Verizon.

AT&T

Nothing much to explain here, as the AT&T offers the same exact trade. An iPhone 4, 4S, 5 or 5C will get you $200 with the 5S getting an upgrade to $300.  Anyone looking to signup or renew with AT&T service can take advantage of this deal regardless of where they got their original iPhone.

Where the difference in AT&T's deal lies, however, is  in the new promotion that allows $100 store credit to get money off of a new iPad. That is in addition to the $200 or $300 from the original trade. Moreover, signing up with AT&T's early upgrade, no-contract Next plan bumps the value to $200 off a new iPad (provided that it is purchased with a two-year wireless agreement). These offers expire on Sept. 30.

T-Mobile

Offering to match the trade-in quotes from the main competition is a good step towards T-Mobile further establishing itself on the smartphone space. Even better, if customers see a better offer from AT&T, Verizon or Sprint within seven days, T-mobile will give them an additional $50 to boot.

This means that users can expect one dollar in addition to the other companies offers. To get the most out of this, customers are going to want to lock in a trade-in with T-Mobile before AT&T and Verizon deals expire on Sept. 30th

Sprint

Everyone already knows about the buyback deal that lets Sprint users get to guarantee its trade-in price is lower than its competitors' prices. This is where users are going to get the most value once the AT&T and Verizon deals end.

Sprint is also offering $200 store credit to essentially earn users a 16GB iPhone 6 for free. To sweeten the pot, anyone that has an iPhone older than the 4 model is als eligible for this offer. This deal extends to any new or existing Sprint users and will be available until Oct. 31.