For years, Verizon and AT&T stayed aloof from the prepaid market, but over the past decade, usage has shifted towards that base, and the big telcos have felt obliged to seek a share of a very large market, and one where higher value services are increasingly part of the mix. AT&T bought prepaid operator Cricket (formerly Leap) in 2013, while the other major prepaid-only provider, MetroPCS, was bought by T-Mobile. Now Verizon has boosted its prepaid activities significantly with the proposed acquisition of Tracfone from Mexico-based América Móvil, in a deal worth up to $6.9bn. Tracfone is the largest MVNO and wireless reseller in the USA, with prepaid brands including Straight Talk, Total Wireless, Simple Mobile, and Walmart Family Mobile.…