Yesterday AMX was reported to submit a bid for KPN which will include a modest premium of 20% over Wednesday's share price:
Slim?s America Movil to Bid for Full Control of KPN - Bloomberg

If AMX gains a majority in KPN before KPN's Extraordinary General Meeting which will vote on the acceptance for Telefonica's bid for E-Plus, they can still avert the sale to Telefonica. However according to p. 8 of this paper it will take at least 80 days until AMX will receive shares and the associated rights to vote. In contrast KPN can hold its EGM 42 days after calling (see Art. 2:115 lid 2 BW), so they could hold the EGM very soon to oust AMX.
I am not sure if AMX may acquire KPN shares on the market during the acceptance period of their bid for KPN and so if they can obtain a majority in KPN even before settlement of the takeover process but if they find shareholders holding 20% or more in KPN who together with AMX block the approval for the E-Plus deal Slim can win this game, which would definitely be in consumers' best interest.