if i am in maxis, can i change to idigi88 but still keep my number?

i am having very huge disappoint with digi now, they promise to me of getting my ipon before tomorrow which is 2 week from the day i booked,
then i try get to them by hp/office# provided on invoice few time, only answer once, i ask them to confirm when i can receive it cause i might not available during these moment, the guy said will check, until now also no reply,

i lost my confidence on digi liao, i use maxis since i was study till work, they got no problem to at least answer a customer call, if next time my phone/service got problem, wth i shud do?

how to cancel i order of switch to digi from maxis and get back my iphone deposit? fyi i booked and change port at jb city square digi not really specialized store...... please help