AT+CGATT=1<cr>
AT+CGDCONT=1, "IP", <APN>, "", 0, 0<cr>
AT+CGACT=1,1<cr> (but you don´t need this one...)
ATD*99***1# (for MC35T, it might be different to you, say ATD*99#)
After this, get a CONNECT string and do the LCP, PAP/CHAP and IPCP negotiations.