Awhile back, we noted that SERO (Sprint Employee Referral Offer) on Sprint was dead and was replaced instead with 'Everything Plus'.

Both plans were attractive for their low price points (SERO was $29.99 a month for 500 anytime minutes, unlimited data/text; 'Everything Plus' was higher at $59.99) but a new twist was instantiated by Sprint: no 'high end' smartphone were allowed on old SERO plans (EP plans are okay). These devices included Palm Pre, Pixi and all Android devices. In fact, the only exempted smartphones were Windows Mobile devices and old Palm Garnet phones e.g. Centro.

It was safe to assume though that when Windows Phone 7 comes out on Sprint, it too would be restricted on SERO, meaning current customers would have to migrate to higher plans, in most cases literally doubling their monthly bill.

Good news though: Starting on October 1st, Sprint is offering 'SERO Premium' to current SERO customers. For an extra $10 a month you can use any previously restricted phone on your SERO account, in addition to getting unlimited GPS Navigation (previously $10 a month in of itself) and 'Any mobile anytime'. For 4G phones (Android EVO and Epic at this time, though we can expect one from Microsoft), users would have to pay another $10, which is similar to that extra $10 that all 4G customers have to pay. While this results in an increase to current customers, it sure beats doubling their costs and we applaud Sprint's move here to continue to grandfather in long time customers.

Current SERO  --> SERO Premium (10/1/10)

$29.99 --> $40 (3G restricted phones)

$29.99 --> $50 (4G restricted phones)

Of course we should note that Sprint has not specifically exempted Windows Phone 7 from this list yet, partially due to their silence on any upcoming WP7 offerings. But we know Sprint is committed to multiple Microsoft devices and there is no reason to think that they won't be exempted.

In short, current SERO customers, hold tight: when Windows Phone 7 launches and Sprint gets some devices (we'll know more on October 11th), you can migrate your current plan over and still enjoy those amazing savings from Sprint. Now shows us your WP7 wares Sprint like, nao plz!

[Read more from Sprint directly here]