Hello buddy , how are you
first wish you a safe travel
second , the phoneUnit is called ( unite) in french and the 4000U means appx. 40,000 Congolese francs ( 1$ = +-910 FC ) , all telecommunication are fine , the cheapest on in the country is Africell for the moment and there's an internet bundle also you may check in all africell shops in kinshasa or lubumbashi , and there's Orange which also has a good area acoverage in the country , as i've experienced the vodacom and airtel has a good internet connection but sometimes it keeps lagging or even cut for a while , check africell or Orange , if you have ablackberry there's a special bundle for those , and if your smartphone is an Android or IOS then the bundle is different, usualaly between 5 to 10$ a week or 15 to 20$ for 20 days . i might be wrong so i suggest you go the shop and ask for offers you may choose yourself.
finally about the place where you looking to rest for a while , there's different places so i suggest you say what's your budget able to pay daily and related to that we can suggest you places and addresses
hope you enjoy your stay in kinshasa
have a safe trip again