for ur call & sms usage, should stay with maxis but change to talkmore48 plan. thats the best plan for u.
but for data, maxis is a little bit expensive and have extra charge after quota

since u want data, umobile28 seems suite u.

b4 u port to umobile, check their coverage at ur place 1st.

umobile28 prepaid free 100mins & 30sms. call charges is 9sen for 30seconds (take it as 18sen/min).

ur usage:
extra 150-250 mins can total up to rm45.
extra 130sms is rm10.40
in the end ur prepaid cost u 28+45+10.40 = about rm83/month.

seems that umobile28 prepaid the best for u. but data only 500mb, not 1gb.

lets look at the options for 1gb:

if u wont exceed that 1gb, then just stay with maxis and change to talkmore48.
talkmore48 comes with free 400 mins & 200 sms to all network (its in ur usage range).
maxis talkmore48 rm48 + 1gb data rm48 = rm96.

umobile postpaid u28: 350 mins is rm70 & 170 sms is free (included in bundle) so total will be rm28 + rm70 = rm98.

celcom (first voice prime rm40): 350 mins is rm52.50 & 170 sms is rm25.50 so total will be rm78, + 1gb rm38 = rm116.

digi (smartplan 1gb rm48): 350 mins is rm52.50 & 170 sms is rm17 so total will be rm69.50, + 1gb rm48 = rm117.50

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Added on October 12, 2012, 3:53 pmor, IF, u dont mind buying iphone and got contract for 2 years, go for idigi plan i88 (rm60/month).
free 200 mins & 200 sms. extra 150 mins is rm22.50 so monthly will be rm82.50