Van ask how your screen is set up at work, V/F’s will work best if the top of your screen is set at approx eye level (this is also the best erganomic position for you too).
With regard to the ‘sweetspot’ issue did you chose an entry level lens or a higher cost one? as on a better lens the ‘usable’ area can be greatly increased,
If it is still within the month and you really cant get on with them most of the major lens manufacturers (again there are exceptions at the budget end of the market) offer to swap you back to a single vision lens for no charge.
PM me or post here if you need anymore details/help