Other networks in Italy a possibility?
 

I just looked up the rates for Italy
and they show three different networks used.
HG3, Wind and TIM.
Are the other networks a possibility for your needs?

I tried and retried all day long. Let me describe the problem in details.
The piranha sim I used, apart from some issue at the beginning when I noticed a certain difficulty registering on mobile networks (already described in this and many other forums) was working pretty ok.
Yesterday evening I rebooted my oneplus 3T (a top notch headset, dual sim, LTE) and discovered that the sim was not receiving any calls. In fact it showed full signal but if I tried to call myself from another phone, the voice said "the number you have dialled is out of coverage". No sms, no outgoing calls too.
I have been in contact all the afternoon with the customer care and even if at a certain point I received one test call from them and was also able to call an Italian landline, in at least other ten calls I could not make the call start.
So I decided to change operator, but to no avail since problems persisted.
I know you are wondering if it's my headset's fault but it isn't. All this morning I used in the second slot another sim card (an Italian sim card) and it worked. I also inserted an Estonian sim and it is actually working.
Customer care suggested me to repeat operations after putting the Piranha in the simcard slot 1 and I did so. Even in this case it is not working.
What I liked most of this simcard where the prices and the US number, since it can be reached at a lower price than Estonians but on the other side I don't want to ruin my beautiful and perfectly working ONEplus 3T phone putting and taking out this sim card trying all day to make things work.
I have reached an agreement with the customer care. Tomorrow morning I'm gonna send the sim back so they can check it. I told them that instead of a full refund I would prefer a working simcard with the same number. I'll specify this in an attached letter and hope they will try to help.
Thanks anyway for your post.

I can't help but believe that some of the reported issues have to do with Piranha's multi-IMSI SIM technology. I suspect that if I took my iPhone 3GS with the Piranha SIM out of the US, where it latches onto AT&T, it would probably start working.

Well, I really don't know what happened but I suspect that the sim was someway faulty due to this strange behaviour. No other hassle with other simcards so the handset is working perfectly. Let's see if they will find what's wrong, I shipped today the sim to UK via registered mail.

VOIP? Has anyone ever "played around with" Piranha's VoIP? You could call a TelnaMobile phone by its SIP address. You could also use Telna's SIP server to make free calls to other SIP addresses. I'm wondering if anything like this is possible with Piranha?

Update: I've tried calling [US_number]@piranhavoip.net and [VoIP_ID]@piranhavoip.net. Neither connected. They both gave Not_Found errors.

I just tested Call-Off-Load in a US to US call.
 

I just tested Call-Off-Load in a US to US call.
Truphone to Truphone---incoming calls free.

I used the STK [SIM Tool Kit] in the phone. NO "+".
[Just tested it again. Did not work with "+".]
Just 1xxxyyyzzzz for both phones.
I think this way [if it works for you] is easier to set up.
1. Put in number you want to receive call at, press OK.
2. Put in number you want to send call to, press OK. Call is set up.

STK call option "Landline callback"

I can't remember this option (landline Callback) in my Piranha sim toolkit. At the moment my sim is going back to Uk for a check, but I remember this option was not present.

Just a question to all forum's members:
do you use the Piranha in a single or dual sim? Mine worked flawlessly (more or less) for a month, then when called, said "out of reach". It has always been used in my dual sim and the customer care says that this malfunction could be due to the dual sim. So my question is: why did it work and then not?

I have used mine in both dual band single SIM phone. Customer service agent is wrong here. It has nothing to do with dual or single SIM. Must be another issue.