problem in arduino uno and sim900 shield gprs /gsm shield logical (rx &tx)

these is my shield , it's right but the logical communication (rx and tx ) between it and arduino uno doesn't work. i think
(rx & tx) supply are 0 & 5 but for this shield is 0 & 2.8 , what am i to solve this problem?

Use jumper wires?

If you had provided a link to the actual shield then the advice might be more specific.

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dannable:
Very similar question on Stackexchange.

solved.