For the sake of simplicity I am assuming that you make 14x 1 minute calls per week, or 2 per day. As you said 5p per minute somewhere in your message I am also assuming you are calling landlines or same network mobiles. I couldn't work out whether you wanted a peak/offpeak package or a fixed rates all day sort of package.
If you don't want to read the boring stuff, my suggestions are at the bottom of the page.
So on Orange you must be on the the "Talk and Save" plan, this is not ideal for low users at all. Based on 2 minutes of calls per day, you are paying 50p per day, this works out at £14.00 per month for just 56 minutes worth of calls. If you switched to the "Fixed Rates All Day" price plan on Orange it would cost you 20p per minute at all times, so your 2 minutes of calls per day would set you back 40p, or £11.20 per month for the same 56 minutes of calls. Finally, if you can confine yourself to talking at off-peak rates, then the "Choose your Off Peak" plan could be considered, basically you get off-peak rates between 11pm and 7am weekdays, and all day w/end and b/hol. You also get a choice of 4 additional off-peak charged hours, which can be taken anytime during the day. So, assuming you talk in off-peak charged times, your 2 minutes of calls would be just 10p per minute, costing you just £5.60, which I think is fairly reasonable.
If you can't keep to off peak times or are intent on switching to another network. Virgin can be considered. Although abit like Orange's "Talk and Save", they charge 15p per minute for the first 5 minutes. If you only talk 2 minutes, it would cost just 30p (£8.40 p/m), cheaper than 2 of the 3 Orange options. T-Mobile has no significant saving on Orange either, your usage would put you squarely in the £10 to 20 price band, which is charged at 20p per minute. Although this 20p per minute is to other networks as well.
O2 Online PAYG "Talkalot" is exactly like Orange Talk and Save - 25ppm for the first 3 minutes. The Offline "Talkalot" is the same. The offline "Original" plan is the same as the Orange "Choose your own off peak" plan - 10ppm off peak, 35ppm peak. However you don't get to choose your off peak hours.
If you are calling specific numbers, then Tesco allow you to nominate 3 numbers for a 50% discount. This brings down call charges to 10ppm at any time, so your 2 minutes a day would cost £5.60 per month.
Finally, Vodafone. "Smartplus" is a peak/offpeak tariff, cheaper than any others covered so far. 5ppm off peak, 30ppm peak. So if you can confine your usage to off-peak hours, you could spend as little as £2.80 per month. Using a 30-day pack will mean you are spending a minimum of £10 but recieve 20 off peak minutes per day (however it might be a little much for your usage habits) "Smartstep" is another of the "Talk and Save" plans, however this is even more expensive - 30ppm for the first 3 minutes.
So! My suggestions. If you can confine yourself to
off-peak hours then choose Vodafone "Smartplus". If you want the flexibility of being able to choose some off-peak hours then go for Orange's "Choose Your Own Off Peak". If you need to talk at
anytime, then I suggest Virgin. The 2 minutes of calls you make a day would cost 30p, cheaper than any other networks' offerings. If you only call
specific numbers then Tesco can also be considered, especially if you want to call at any time.
Current Orange: £14.00 per month
Switch to Smartplus: £2.80 per month
(Based on Off Peak calling Only)
Switch to Orange Peak/OffPeak: £5.60 per month
(Based on Off Peak calling Only)
Switch to Virgin: £8.40 per month
(Anytime)
Switch to Tesco: £5.60 per month
(3 Nominated Numbers Only, Anytime)

Good luckl!