Ally (D20 Modern Feat)
From D&D Wiki
To gain the ally’s aid, you must address him personally or get a message to him. The GM then makes an Ally check. To the roll result, he adds 10 + your Charisma modifier + any modifiers based on the situation. If you have recently done the ally a favor, you may get a +2 on the check. If you recently risked your life for the ally, you may get a +4 or +6 on the check (GM’s discretion).
The DC depends on the type of aid asked. If it’s a simple request for an ornithopter ride or dinner invitation, the DC is 10. Asking your ally to introduce you to one of his friends or even rivals might be DC 15 or 20. Request for military aid would be 25 or higher, depending on the nature of the ally (priests can rarely supply troops).You may make a request of the same ally once per month. Two successive months of such requests causes the DC to rise for each successive attempt. Should the DC ever get as high as 40, that ally will no longer heed your requests until at least a year has passed during which he has no requests from you—but he might ask you to perform favors to bring the relationship (and th DC) back to normal.