Nataka simu mbili ziwasiliane

[Allency]

Habari zenu wana JF, nina room mbili ambazo nataka watu waweze kuwasiliana kwa kutumia simu za kawaida (landline) ila sina ufahamu wowote juu ya nini natakiwa kununua tofauti na extension mbili, yani the cheapiest way as possible. Nmesikia kuhusu kitu kama PBX but i dont wanna go for that. Its like i want plug and play or something like that. Any advice will be helpful to me. Thanks in advance