I can't quite figure out what you are wanting to do, but for those that are trying to help here is a dataset you can use.
library(dplyr)
library(tibble)
AllData <- tribble(
~C_ID, ~M_ID, ~max_ad_date_id, ~max_DIS_DATE, ~SER_C_DATE_ID, ~CL_CCT_IND,
102472781, 3874931, "24/05/2015", "28/05/2015", "24MAY2015:00:00:00", "N",
102472781, 3874931, "24/05/2015", "28/05/2015", "24MAY2015:00:00:00", "N",
102472781, 3874931, "24/05/2015", "28/05/2015", "25MAY2015:00:00:00", "N",
102472781, 3874931, "24/05/2015", "28/05/2015", "25MAY2015:00:00:00", "N",
102472781, 3874931, "24/05/2015", "28/05/2015", "25MAY2015:00:00:00", "N",
103011920, 3998668, "28/01/2015", "28/01/2015", "28JAN2015:00:00:00", "Y"
)
AllData <- AllData %>%
mutate(max_ad_date_id = as.Date(max_ad_date_id, format = "%d/%m/%Y"),
max_DIS_DATE = as.Date(max_DIS_DATE, format = "%d/%m/%Y"))