Americans are subscribing to cellular telephone service in droves, boosting the total number of US customers to a record 19m, the Cellular Telecommunications Industry Assocation reported in its mid-year survey, which shows that in the first six months of 1994, the number of cellular subscribers grew by 3.3m, the largest ever such rise; the data, compiled by accountants Farren & Lanman, showed that the industry signs up more than 17,000 new cellular customers every day, but the average monthly cellular bill dropped to $58.65 in the first six months of the year, down from $67.31 the year earlier and from $85.52 five years ago, it found; in the year to June 30, the industry generated $12,600m of business, up from $9,000m in the 1993 period.