GSM 850 MHZ with noise ?

Product : Quality of call Service.
Part Involved : GSM 850 MHz
Summary: The quality of mobile call party has been degraded.
Scenario : Mobile call party has a lot of noise inside of main building of MINSA (HQ).
Company : Ministry of Health of Peru (MINSA).
Reference Date : April 2007.

I contacted with Telefonica of Peru (Mobile Carrier Operator) because my co-workers were sure that the source of the problem become from the mobile phone itself but I did not think the same -I have another track with my RF experience-, a few weeks ago I came with personnel of Telefonica on the roof of the main building office of the minister of health (MINSA) -5th floor- (on below picture painted with light blue) and the RSSI readings were from 90 and 85 while at the same time we tried to locate viewline from cellsite to here and we founded : Garzon, Milan, Beatriz. (upper picture is Milan Cell Site).

Additionally the list of traffic channels captured from here shown that noise and interference added to call party become from neighbor Cell Site traffic channels - That is following through engineer mode of mobile phone, please check http://germanmedinavirtual.blogspot.com/2007/06/engineer-mode-in-mobile-phone.html -: that is to resolve that It is necessary to reassign the group of traffic channels belonged to the set of cell sites involved into area described. This goal enhanced powerful -procedure called into mobile technology world as performance- the quality of the call party (according to the frecuency plan of the city of the carrier operator) and now the RSSI reading from 4th floor (inside the building) reached from 65 to 77, in another words is a nice calling. The traffic channels taken basically from here belongs to Cell site "Lawn Tenis" sector 3 painted with line red above of the light blue block on the map.